I bought a concertina years ago and back when I first got it I kept having a button stick so took it back to the music store for a repair. They opened it, couldn't find an issue, and after they put it back together it was perfectly fine. Forward to now after the instrument has been sitting for a few years, I started to finally learn how to play. Unfortunately, the issue came back on a different key. I went to open it to see if that would fix it, but a couple of the heads got messed up. I know I used the right screwdriver since I went to a hardware store to find the right one and I also know I didn't use too much force since I have a disability in my arms (a large part of why I wasn't able to learn over the last few years) so can't produce enough force to damage a regular screw. Any way, I now have 2 ruined screws and want to replace all 12 to be sure this doesn't happen again.
The screws are 1 x 1 3/4 oval head chrome brass screws for a Musician's Gear 20 button Concertina. If you google "red concertina" then you're almost certainly looking at the model I have. Due to the shape of the screws I haven't had luck at hardware stores, the music store I bought it from, or finding out how to contact the company directly for replacements so signed up to see if anyone here knows where to get them. Please let me know if you do or if you have a theory about my original problem.
Thank you for reading and any help this can lead to!