I too have been frustrated while looking for a DVR. I found one that held 310 hours of recording, had a USB adapter for PC downloading, editing capabilities, and several other nice features all for under $45 at Wal-Mart, but it didn't have a microphone adapter only a built in one. The only one I found with a corded microphone was crud and only held 1 hour with no USB download feature.
If anyone here hasa DVR that has the external microphone and a USB adapter. What brand is it and where did you get it?