RuntimeDNA.com has sets of armor for the Mil figures. Not free, though. But they usually have a 50% off sale in the fall.

PoserPros has samurai armor for M3 and David. The M3 version sometimes is in their freebie section (during the buy one, get one free sale).

And there's some very nice samurai armor here in the RMP. It's for M2, but M3 can wear it, if you use the M3 to M2 figure.