I have an old Craftsman dial caliper that does the job (the same type is sold under many names) but I wanted a second set that I could just leave my comparator attached to. I saw this on Ultimate Reloader and decided to try it on Gavin's recommendation. Under 30 bucks and lots of great reviews. So far, I have zero complaints.
https://www.amazon.com/iGaging-Elect...35147515&psc=1