If you're looking at that level mic, you probably want to get into some of the "semi-pro" level recorders.
In particular, the Tascam DR-07 has gotten very good feedback from users within the digital video community. It runs on 2xAA cells, and records on SD/SDHC cards. I've been quite happy with mine. The original DR-07 had separate mic and line inputs, but I believe it's been discontinued. I have heard that the new version (DR-07 mkII?) has only one combined input (which of course is a ridiculous concept).
The Tascam DR-03 is considerably smaller and more convenient. I've been very little feedback, but it has been fairly good. It runs on 2xAAA cells, and records on micro SD/SDHC cards. I haven't used mine very much, but it seems to be decent.
Tascam also makes a DR-05, which I haven't seen, but which appears to be somewhat similar to the DR-07.
All of the above have reasonably useable integral electret mics. and also unbalanced mic inputs on a stereo 3.5mm jack, with "plug in power" supplied to run consumer electret mics.
Where did you find a list of recorders that record 44.1 PCM/WAV with Rockbox? If any of those are smallish flash memory machines (as opposed to HD storage) I would like to check them out.
Thanks!