Ebay site. I have no affiliation, etc; I bought one the other day and used it tonight at Augustine's Club 17 up here in Old Forge (review to follow in new thread).
I don't know if any of the joints are any good, since I don't live in Philly.
If you don't feel comfortable bidding on ebay, you can go to the home page and buy the certificates outright for 1/2 price. The one I bought was bid up to $7.
I hope it helps.