Check keh.com or mpex.com to see if either store has one. I've personally never dealt with these places but they sound like pretty decent stores. Calumet has a used department too.

In any case, the price that they will charge would probably be a little higher than you might find it for on ebay. Hard to guess a used price versus new - some things seem to sell for just slightly less than new (like pro lenses in good shape), some things for much less. If there aren't many out there, then you might only find a used one for close to the new price. If that's the case, you might want to stick with a new one - warranty reasons, etc.