A few years ago when I started to look into the quad situation, you were very helpful to me. Eventually we bought an uncoupled quad from Santana. We are a few years behind you, so our current picture is more like your old one...
Giant OCR1; Fisher Paragon 29er; handbuilt MTB based on IronHorse Race frame
Nice to meet you Mark. My wife and I just bought our first tandem this past Saturday. After a vigorous 2-month search for something used, we ordered a Co-Motion Speedster from Tandems East. They have a great inventory, but you probably already knew that.
You didn't mention what you'll be looking for - maybe you can share you search parameters here so folks can keep an eye out for you.
Good luck with your search, and welcome back to the tandem world.