For my floor demo model Ridgid table saw I used very thin brass sheets picked up at the nearest hobby shop... Still works great, even after being disassembled for moviong and re-assembled.
BTW, since the instructions for setting up my saw specified shim washers, I worked out a slick method of cutting my own shim washers:
Sandwich the shim stock between two boards and screw or clamp them together. Then layout and drill the center holes to match your bolts. Next use a spade bit with cutting ears out the outer edge to cut the outer diameter. This is best done on a drill press and you need to pay careful attention when using the spade bit because the shim stock will tear easily. However, after shredding the first few attempts, I was able to make more than enough shim washers in about 15 minutes. I retrospect, I may well have just slipped the shim in near the bolts instead of making washers....
Chris