microphone for Olympus C-770

My Olympus C-770 has a built in microphone which works pretty effective for
table side conversations but on occasion I want to pick up the sound action
at the granddaughters recitals, sports events, etc. My local Olympus dealer
does not carry any microphones and the local radio shack only had
microphones for singing, dictation, etc...

And experience/recommendations out there for a microphone that does not
block/squelch background noise that I want to pickup? The "jack" on the
camera is a 1/8 inch but I suspect I could get an adaptor.

w