We are waiting to see if EliteKeyboards.com can get blank black keys from Filco (and possibly black and white replacement keys w/ legends).
As far as the special red Esc, blue/purple WASD, and yellow function keys, I think the best bet is from a place like Signature Plastics, but I imagine the cost will be high, even if we get 20+ people.
As far as Topre, your best bet is ordering those from a distributor overseas. The HHKB blank keys should work, as far as I know.