I found an Epiphone Blues Custom 30 on Craigslist for cheap, but the seller says it needs a new power transformer. How much would one of those cost, and how hard would it be to replace?
I think that may cost you at least maybe $200.
Check Mercury Magnetics, or Heyboer. A tech there could probably tell you exactly which model you need. You're looking at $50- $200 depending on where you can get one. Replacement would not be too bad with some electronics and soldering experience. But a tech should do the job for no more than $50 bucks, unless he's ripping you off.
Boom ch ka!