The Taxi DVR searches resulted in equipment recording from fewer than 3 sources (4 would be ideal). I did find a cheap DVR for $50 with pretty good reviews and working with 12 volts at 2 amps, which is very good for the car environment. Unfortunately, it will NOT work with a hard drive that is less than 500 GB. While such an HDD is easy to find, HDDs are vulnerable to vibration and their operating temperature is generally 0 degrees Celsius (freezing point) and up. Every year the temperature where I work drops below that, often significantly below that, which is why the laptop I use uses a small SSD, which has no mechanical parts and is therefore not limited to the temperature ranges of the older HDDs. A small SSD that I use is more than enough for me to record what I need, but the size of it is either 32GB or 64GB, I forget which. It is fairly cheap, but getting an SSD sized 500 GB or more is prohibitively expensive so that idea is not feasible.
I am looking for something small, simple (on button, record button), and cheap. I don't need to have the ability to play items back from it. I can do that by taking out the storage media and putting it into another computer. I also don't need to store anymore than 10 hours of video.