I would suggest posting in other Craigslist listings for any major city within 3 hours of you...you have quite a few of them. I'm over in Indy and am getting ready to drive 3 hours to pick up a tandem I purchased (that I also found on the Tandem Mag classified site). Finding the right used tandem takes some time (it took me over a year), so people can be motivated to drive a few hours for the right one.
You might also try the Central Indiana Bicycling Association website (
www.cibaride.net). They have both a forum where you can post it as well as a link to the HOOTS (Hoosiers Out On Tandems) website where they also have a classifieds page (not sure if it is for members only or not)...