Actually I remember reading that the bearings were in fact the same as the ones currently in the cups (as pointed out previously)...just without the cups. If that's true then you can pick up any of the bearings you see anyone selling as replacements for Shimano cranks.

Enduro has some decent priced ceramics if you are interested (around $60 I believe). Also I remember Competitive Cyclist selling a Phil Wood spec'd replacement (standard catalog bearing).

I have notes somewhere that show the bearing number. If I find them and post then you can just order a set up through McMaster or Grainger or MSC, etc....