Dec 05, 2007 05:37 pm K-Micro from Karma Audio. www.karmaaudio.com/kmp.html
I reviewed these a little while ago and used the higher SPL version on some brass with great results. For a cheap little mic it gets much higher dollar sounding results.
Otherwise the only other clip ons I have ever used are the little Shure units. Can't recall a model at the moment though.