You could try a local accordion repairman. They will often have second-hand accordions available.
None of these places is a sure bet, so be sure to call before you go.
Gelman Loan Co.
6490 Frankstown Ave.
661-3818
Main Loan Co.
503 E. Ohio St.
231-1155
Pawnshop On the Corner
789 Penn Ave.
Wilkinsburg
243-5550
Pitt Loan Inc.
603 Ohio St.
321-2500
Steel City Pawnbrokers Inc.
635 Braddock Ave.
Braddock
271-7454
Johnny B. Good's
Used Musical Instruments
801 Chartiers Ave.
McKee's Rocks