UPDATE- see edit #2 below for workable solutions.
Joined here to get some info on this now non-existent part, and to hopefully create a path for others that want to use something similar. Since this thread is relevant, I'm adding to it vs starting a new one. I sent an email to the CalSci place that says they are developing one, but have not heard from them. My 1992 GSX1100G has added Prosport oil pressure & temp gauges and I need a place to mount the senders. The pressure sender sticks out too far to install on the main gallery on the right side of the engine, so I'm looking into using a filter adapter (sandwich) plate that has the 1/8 NPT openings in place. Since I have adapted AN fittings to the front oil cooler lines, it looks like I have enough room to mount the 3" diameter plate there.
To mount it, it attaches to the existing pipe where the filter attaches. Since our bikes use an ultra-fine and unique 20x1.0mm filter thread, no one makes an adapter for that one. Standard thread here is 20x1.5 with other SAE and metric options available. The 20x1.5 filters generally use the same base/gasket dimensions based upon my research at the Wix filter site. My first question was what is the thread size on the block end of this adapter? The adapter is still available as Suzuki PN 16591-06B01. In lieu of buying one, I pulled one from a 1991 GSX1100G parts bike I have. I found the block thread was a common 3/4-16. The adapter is about 1.25" long. I took some pics of it and will attach them for reference.
Now that info is known, the next issue involves finding an adapter that is 3/4-16 x 20x1.5. I looked up some common Japanese bike adapters and here is what I found:
Most Hondas use PN 90019-MB0-000, which uses a 20x1.5 filter. The block end is unknown. It looks similar to the Suzuki part.
Most Kawasakis use PN 32033-1535, which is 20x1.5 straight thread. No go on that one.
Most Yamahas use either 90401-20008-00 or 90401-20007-00, with the latter being used on mainly boat engines from what I can tell. These both are 20x1.5 on the filter side, and unknown but different on the block side. These unlike the Hondas or Suzukis have a hex fitting to remove & replace them.
My plan is to pickup these adapters and measure them. Best case scenario, one of them will be 3/4-16 and screw right in. If not, then a pan B will be in order, perhaps just a length of 3/4-16. The drawback there for usage w/o the plate would be finding a filter with the proper base size. I will update as I make progress on this project.
EDIT
While browsing, I learned the AN8 fittings use the 3/4-16 thread needed. To use this, the AN seat could be cut off flush with the threads. There are a number of aluminum adapters to adapt AN8 (1/2" JIC) to M20x1.5. Finding one in steel was a little more challenging, but I found one here: https://www.discounthydraulichose.com/9067-08-20-12-jic-male-x-m20x15-metric-male.html
To test this idea, I used an old AN8 to 1/2 NPT adapter I had in my shop, and installed it on my parts bike motor. I was able to thread it in perfectly, and had to use a ratchet & socket to tighten it. Since the fitting has a hex, it was simple to use a 7/8" or 22mm socket to install & remove it. I'm unsure how the hex would affect those that just want to run a filter though. It may prevent the filter from sealing. The Bales adapter has no hex, so I think this may be the case. If I end up trying one of these, I'll connect an OEM filter to it and see how that affects sealing.
EDIT #2- Solved
I found the Trans-Dapt #1034 oil filter nipple on Eblag for about $6 shipped. It's a 3/4-16 part with segregated sections and no hex just like the OEM part. I downloaded Wix filter data since they offer it by thread size, and found there are more compatible filters in 3/4-16 than M20-1.5. Since my adapter plate has both 3/4-16 and M20-1.5 fittings, I'm going to try this part.
While browsing, I did find what appears to be a 3/4-16 x M20-1.5 adapter made by Mocal, PN TN3/4XM20. The only place it is available is BAT Inc. in Sarasota, Florida, a site that deals mainly in imported cars (BAT is British American Transfer). The page with the adapter is here (PDF file). That site does not accept online orders, you have to call them. They also have a handy page here (PDF file, pages 12-14) that lists filter thread sizes for many years & makes of cars as well as filter sizes by engine model.
Filters
Wix allows you to search filters by thread size here. From the first drop-down, select the Lube, Hyd, Trans, P. Steering, Torq. Converter line , then select Spin-on Lube, Hyd, Trans, P. Steering from the next drop-down, then select the size from the page that loads.
For 3/4-16 filters, the Wix 51395 is less than .2" longer than the OEM Suzuki filter, it has the same gasket dimensions, and the bypass PSI is listed as 8 vs 8-11 for the OEM. They also make a 57890 that is .6" shorter, but has the same OD and gasket. I will likely try that one since my plate will add about an inch to the height.
For 20-1.5 filters, the Wix 51358 is the exact same size and gasket data, but it has the same 8 vs 8-11 bypass spec.
Either of these can be crossed over to your favorite brand of filter, I was just interested in dimensions and gasket sizes.