Your best bet is to look up Second Hand Building Materials in the Yellow Pages.
Here are a couple of online places.
Select Salvage - Recycled / Second Hand / Used Building Materials, Supplies. Windows, Doors, Entries, Fireplaces, Period Pieces.
Hughes Renovators Paradise | Second Hand, Recycled & Used Building Materials, Supplies. Windows, Doors, Entry Doors, Front Doors & Fireplaces
Regards Dave