EFE gear selector switch is about £60.. from robinsons or fowlers
2nd hand Garry Hurd or Chris Tombleson should be able to help
its used on a few models trawl the part no on a well known site
I fitted a set to this years ago...no heat just used some wooden wedges to spread 1 & 2 and the same on 3 & 4 and i used 2 suzuki gaskets in each port as the thou headers are a smaller bore and prone to blowing
i would add that using the correct clutch lever and perch makes a big difference a longer cable "faired efe is longest" can also help dept on what handlebars your using ...
we used to reclaim damage like that by fitting a copper bar into the hole and then build up the ali casing around it with weld then remove the copper bar and could often get away with out any major machine work