I've often had to get these apart to replace bearings and just used a punch/screwdriver without a problem. Appreciate you'd rather not take the risk, and looks like it might be a Makita so it might be worth contacting them to see if you can buy the tool as you can usually buy every part you...
Never seen those but given you've got the blade you could always give it a try on some brickwork within the area you are ultimately cutting out (so it doesn't matter if it makes a terrible mess of it). I'd guess it won't produce a clean cut like a disc and may pull at the bricks, but you never...
These have been used in the jewellery industry for many years due to the powerful fine flame. Look up jewellery micro welder and you'll find them for sale. They're not practical for larger work really.
If you have access to the back and that area isn't painted / doesn't matter about a perfect finish then perhaps you could chisel / grind / use an oscillating saw to remove the deformed side of the rivet.
My thoughts are it might be best if you get a fresh plate, clean shiny metal, lay a couple of welds down as straight as you can (scribe a line to follow) and for as long as you can, then post a pic.
I have a fairly heavy but hand held belt sander that I have used with a coarse belt for longish runs of alu weld that needed to be flush. Makes short work compared to anything else I tried.
^Sorry will I meant to post this to a similar Q about aluminium welds. Don't do this on your stainless! I find it best to go carefully and really avoid marking the sheet metal as much as possible if you want a really nice stainless finish.
Will, I may get flamed for this by those more knowledgeable, but I have a fairly heavy but hand held belt sander that I have used with a coarse belt for longish runs of alu weld that needed to be flush. Makes short work compared to anything else I tried.
How have you been 'testing' for leaks? Cup of soapy water (washing up liquid) and brush on everything. You'll see bubbles if there's a leak. Sorry if stating the obvious.
Yeah I see your problem Hugh. You'd think there would be more available with the number of people who have to wear ear defenders for long hours day after day.
Sorry if this is already suggested as I skimmed the thread... Have you considered buying any regular ear defenders you like, then using some wireless headphones / airpods. Slightly more hassle to put on of course.