Most recent Recumbent and Tandem Rider Magazine (issue #43) lists 20+ used tandems for sale in their classified ads!
Alphabetically ranging from Burley to a Yakota Twin Peaks; several recumbents and even 2 recumbent trike tandems . . . plus a triplet!
Prices range from $600 to $5,900.
Also some good tandem and recumbent articles + a daVinci Joint Venture review.
www.rtrmag.com