Magnavox makes some for $300 and less. They only record in 480, but will upscale to 1080 for viewing. The SD recording has stopped me from getting one. My parents use a similar model from Panasonic that I got them years ago and love it.
Channel Master at least used to make an HD DVR for OTA, but I don't see it anymore (didn't look all that hard, though). It was too pricey for me when it came out and I forgot all about it. You might still be able to find one.