Creative JB3 seconded. I have used mine for live recording for almost two years. I bought it from Creative on ebay as a refurb. The optical digital in, WAV recording, no media to buy, firewire transfers, and not a bad onboard ADC make a winning combination. taperssection.com is a great board to learn more. I don't think you could get a functional JB3 for $100, but if you stretched to your $150-$200 limit you'd have no problem. However, there is no mic power or usable mic preamp, necessitating additional external equipment. Do you already have a mic(s), mic preamp and power supply?
DATs are fussy (heads require maintenance, realignment, and replacement), expensive, and require real-time transfers. That being said, most high-end tapers I know still use DAT (or laptop), FWIW.
MiniDisc seems like a great solution at first. These little units are robust, small, cheap on ebay, and many have great battery life (50+ hours playback).
Click here for tons of specs (I wish there were a headphone database like this!
). Media is cheap. Most (but not all) feature a Mic In jack with ok-to-fair mic preamp with a small amount of mic power (typically 3V, but most mini mics require 9v for full performance, and many full-size mics require 48v). So, unlike a JB3, a MD can be a one-box solution: you can really just plug in some mini mics and go.
But, with regular MD, real-time analog transfers (to PC) are a downer. Digitial transfers are possible, but require one of a minority of home decks that have a digital out. Also, MD (ATRAC) is a compressed format to begin with.
Hi-MD could be a cool solution, with digital transfers of your uncompressed recorded material and a larger disc, but they are pricey. And blank Hi-MD's are expensive (~$6-$7 each).
I've really enjoyed my progression of MD decks. They are a great little gadget and is still my backup listening/recording rig. I still use it for travel recording, because mine (like many older models) uses 1 AA, not some fussy proprietary internal rechargable either alone or in tandem with an external AA.
There are probably several other options, if MP3 would be suitable for your use. Check out
http://www.cowonamerica.com/products/iaudio/u2/
, with a line-in. Headfi-er's Asr and lumanogin each have one, perhaps you could PM them and ask about the recording functions.
Keep us posted in this thread about how your search progresses! I am very curious about new options in digital field recording.