They do sell off demo saddles. The main phone number is here: http://www.countysaddlery.com/. I know it says call to schedule an appointment, but that number is for everything. Just call and tell them what you are looking for.
I have found quite a few used ones on TackTrader, EquineHits, HighEndUsedSaddles.com (or FineUsedSaddles, one of them carries them, the other doesn't) and eBay. County reps have lots of used ones floating around though.