Shims for flm ultimate hybrid rear bulk

[Xcaliber]

Hey guys I bought the new brushless edition emaxx and have been upgrading it.. I bought the flm ultimate rear bulk and put the 1/8 diff that it cimes with inside the housing and noticed that it has enough play left to right to make the center yoke to not spin, I have read the how tos to shim the diff to get it right but my problem is finding the right shims to buy. I measured the I ne shim it seemed to come with and it had a 15.875 diameter. Anyone know where I can buy shims for this diff to solve the issue? Thanks!!