don't mind me while i try to make a sale here
http://www.taperssection.com/yabbse/index.php?topic=26377.0i bought these as a step up from my sony ecm mic back in the day. and they were a huge improvement. if i were you, i'd go for a battery box, it might be a bit of a pain, but really, its worth it. with the battery box the mics can handle higher SPLs (sound pressure levels) and they'll sound a lot better. these are omni's, which means they'll pick up things around them, however, i've taped many a concert with them and have never really had problems with them picking up the conversation of the people behind me. I'd usually always wear them in binaural fashion - clipped on the bill of my baseball hat right where the bill meets the hat itself and they worked like a charm.
I'd let them go for $80 and I'd pay shipping. Its a bit more than $50, but I think you'll find it to be worth the money. These are dynamic audio mics, and in my opinion they sound better than the giant squid mics - but thats just my opinion.
I ran these right into my nomad jukebox's line-in, if you'd like to hear some samples...
http://www.archive.org/audio/etree-details-db.php?id=8784http://www.archive.org/audio/etree-details-db.php?id=12999...there are some plus a bunch of others in the fuzz section. good luck and happy taping.