Mic Stands. Stability is key and a mic stand with a tripod base will give you the best results. Retail $25 to $75
Small Instrument Microphones. The Shure SM11 is a small dynamic mic that sounds great on harmonica, works great on stage, and doesn't need power. Most other small, good quality microphones are condenser mics and I find they are actually too sensitive and will pick up too much vocal along with the harp. Average retail $120
Mounting the Microphone. The Audio-Technica AT8418 UniMount works great. It's a little tight, but the SM11 microphone I'm recommending will fit into this UniMount pop screen. Average retail $32
I snip off the gator clip from the UniMount and then use two zip-ties to secure the UniMount gooseneck to the Harparatus boom arm just below the sound baffle. Presto! Now your fun begins.