Shoot an email to Dan Schultz (http://thevillagetinker.com/) and see if he might have some lying around. Also, you might ask him about the feasibility of using valve cluster from some other brand (assuming you aren't trying to do a fully restoration to original).
I'm curious what "not repairable" means since if they only leak, I'd think that repair is an option.
Gary Merrill
Wessex EEb Bass tuba (DW 3XL or 2XL)
Mack Brass Compensating Euph (DE N106, Euph J, J9 euph)
Amati Oval Euph (DE 104, Euph J, J6 euph)
1924 Buescher 3-valve Eb tuba (with std US receiver), Kelly 25
Schiller American Heritage 7B clone bass trombone (DE LB K/K10/112/14 Lexan, Brass Ark MV50R)
1947 Olds "Standard" trombone (Olds #3)