Bacon''s has a great selection of sails and many are in very good shape. You can search their online listing...very nice feature.
One note: many of the used sails you will get at a good price will need some work. That CAN be as expensive as the sail. Chose your sail maker carefully and discuss and agree to price in advance. Don''t bother to get it washed... that is very expensive and of questionable value (do it yourself).
Hope this helps.