If you are still looking for an inexpensive dulcimer with decent sound, let me tell you of one I have. I own about 20. In the process of purchasing them, I purchased one I thought would just be
a novelty, but it amazed me that it had such good sound. Not like a
McSpadden, or course, but something you could make music on. It was
on ebay, and listed as a TN Music Box. It is from "Off the Beaten Path", and "American Dulcimers". It is rectangular, and is made of real wood.

It doesn't compare with the best dulcimers in workmanship, but for the price, I thought it was a good 'student dulcimer'. They list for about $120 on their site, but there is one on ebay today for $59.99, (a buy it now price) plus shipping. There is a picture, and some good information on the ebay site.

If you have trouble locating it, just do a search for "TN Music Box".
For the purpose you have stated, it might be something you can use.