Just got in this set of AMAZING custom shields from Spy Monkey Creations. Each shield is $10, which is a great price considering that these are all hand-made, custom casted pieces. There are 5 shields in all, with a different stone/ color variation to differentiate from the other. While these aren't specifically listed as being made for MOTU Classics, they fit great and really match certain characters quite well!
(And yes... that's a custom head on ol' boneface...)