It looks like the cheapest option for new caps (at least from WASD) would be to get:
- 87-key set ($37 blank, +$10 labeled)
and
-(4) numpad "+" keys ($1/ea.)
or
- (2) "+" keys ($1/ea.) and
- (1) Row-4 1x2.00 key ($1.25)
The 87-key set will provide (2) 1x1.5 keys and (7) 1x1.25 keys sufficient to cover the ErgoDox's (8) 1x1.5 key spots with some slight edge gaps, or you can add (10) Row-3 1x1.5 keys ($1/ea.). The 87-key set includes a cap puller and enough spare F-keys, which the ErgoDox won't use, that can be used to fill in keys as needed. (Hm, I wonder if WASD would be willing to offer an 87-key labeled set with blank F-keys upon request?)