I would recommend going through the number of threads on the Mudcat that discuss the Minidisc. It's quite informative.

I would recommend any of the minidisc models you like the look/feel of as long as it has a Microphone input. Most current Walkman type portable MD recorders don't have microphone inputs, and they do cost more. However, you CAN purchase one of the many which don't have such as LONG as you purchase a microphone (none of the ones I know COME with one), with a PREAMP to bring it up to Line Level. Apparently not ALL MD recorders have the Line-level in, so you might want to look and make sure.

In one of the previous threads I posted links to microphones with preamps.