Yeah, a decent minidisc recorder is a perfectly good substitute for a DAT in most cases. Sure, it's compressed, but if your locations are quiet enough for you to notice a sound quality loss from the compression, you're extremely lucky! Similarly, you can record sound direct to DV with no problems in most cases, though a seperate recorder is useful for getting atmos tracks, effects and the like.
Otherwise, my DAT walkman cost about $700, I think: sound quality is fine (though there's no digital output), but it's not very robust. Real, solid, location DAT recorders that your PAs can kick around and drop without breaking are generally up in the thousands of dollars.