You have accurately described those screws. Crappy...The General must have only intended for them to be in the "one time use only" catagory. You should be able to get them at any GM dealer, and dont be scared to pay over a buck a piece for them, thats gonna set ya back 2-3 dollars, so whoopty doo, if ya know what I mean.
You can try looking for them in places like Autozone as well.

Good luck.