If I were you I would try using bug mics. I play in a celidh band and the bug mics fit under the fiddle bridge quite well. They also give a good sound. If you put a couple under the bridges near the sound holes it should work. I think that the idea of 'plug in and play' is good but due to the mic being fitted into the interior it means you get the sound from inside the dulcimer and not what the listener hears.

I hope I've been of some help

Bye, Sam