You may want to check with some Old Town Canoe dealers. Their web site has a search capability for your area. I saw several used Loons (can't remember the models) earlier this year at Fernald Marine in Newbury, MA.
For other options, check this for a list of links to used yaks.
http://www.kayakonline.com/used_kayaks.html
I'm looking too and have found the most listing posted on the link to paddling.net.