Save some cash, battery hassles and get just as good a camera as an OM1, buy a Pentax MX. They are cheaper, as nice, and take standered akaline or silver oxide batteries.
I love mine use it and an ME Super all the time. I second the canonet though, love it as well.
K-mount lenses are great, fairly cheap, and go from 17mm- 1000mm. The MX is a Pro camera, offers interchangable focusing screens, motor drive, fully manual operation at all speeds, PC socket, and a hotshoe. You really cant go wrong with this camera, and it is about the same size as the OM-1, esspecially with the 40mm pancake lense.