How about putting an ad on local craigslist, or facebook marketplace? That way you could try it to insure it works (just bring a points car that you know the dwell, or, risk the 5 or 20 bucks it might run.
Over the years I've picked up a few at garage sales. They all read just about the same. I have my first one a RAC 560 that I've had since early 70's still works fine (although I always thought it "cheap junk") .
Craftsman are generally a good name brand in their wrapper. My favorite is an small old chrome sun branded.
Keep in mind many are just sitting around not used by homeowners.