i forget where i got it from, sears of home depot but the General brand ones arent too bad for just quick measurements, and i think are right around $30 so you dont have to worry about it too much. there are only 2 decimal places so its not going to give you hugely accurate readings for minute tolerances. the next step up in my opinion and what we give as a supplementary caliper in our field service kits are Fowler brand, a little more expensive but much more accurate, followed by Mitutoyo which are more money, more accurate and are our primary ones both in the lab and for our field service guys.
i have both a couple sets of general calipers in the garage and home and a set of mitutoyo, general ones get used more simply because i usually dont need the mitutoyo's in my day to day and i dont want to subject them to possible damage if i dont need to.