If you've confirmed that the bearings actually come out, have you tried the bike shop you got the bike (or the headset) from? Failing that, look online. The details of the bearing dimensions ought to be printed on them somewhere.

If you haven't already pulled it apart, I don't know if the Ritchey headsets have the removable cartridge bearings or not, but if Fietsbob's right and they don't, Chris King would be the logical option provided you can afford to spring for one. It's the exact antithesis of "buy cheap, buy twice".