Yep, McMaster has them in 18-8. Leveling washers they are called.
18-8 Stainless Steel
1/4" 0.312" 0.875" 0.250" 0.125" Rockwell B45 5 90845A010 $12.12
5/16" 0.375" 0.875" 0.250" 0.125" Rockwell B45 5 90845A015 13.03
3/8" 0.438" 1.250" 0.312" 0.125" Rockwell B45 1 90845A037 6.11
1/2" 0.562" 1.250" 0.312" 0.125" Rockwell B45 1 90845A038 6.11
5/8" 0.688" 1.500" 0.375" 0.125" Rockwell B45 1 90845A039 7.04
3/4" 0.812" 1.500" 0.438" 0.188" Rockwell B45 1 90845A040 7.65