Stargateprops.com have begun auctioning for sale rare and one-of-a-kind costumes, props, and other memorabilia from the Stargate: SG-1 series, on their own internal auction site. Over 60 items are currently up for bid, with a promise of many more to come as the studio begins to empty its cache of SG-1 items and send them to Stargateprops for sale.
All of the Stargate items are listed here. Click on a category to see the items in it, for example, costumes are here. The prices are very reasonable for some of the items, and Stargateprops is a very reputable company (also known as Legends Memorabilia).