Hi Leigh,
The odds of finding reclaimed/used doors that fit all the proper size constraints is EXTREMELY small. Even finding new doors that match the exact style of your base cabinets will be a challenge. Your best bet is likely to find a custom cabinetry manufacturer (local custom shop) and show them a door from your current base cabinets. They should be able to tell you if they can build/find a similar enough door style. The next challenge is going to be refinishing the bottom cabinets and getting the new finish on the new wall cabinet doors to match. The custom shop should be able to tell you if they feel they can get those things close enough.
It seems counter-intuitive, but you may want to consider replacing all of the cabinets (or at least all of the doors/drawers) so that they all match.
I hope that helps at least a little!