A common digital voltmeter will do everything you need. Quality should be reasonable since you will be sticking this thing in electric sockets.
You should be wary of the 3-light testers. While they do provide a simple pass/fail test for most outlets, the legend describing the likely faults for "fail" conditions are misleading and wrong. Many hours have been wasted because people believed the legend's interpretations of the fault. I just saw a labeled "hot-ground reverse" which was in fact a lost neutral. (night and day, like reporting a bad fuel injector when the problem is actually a flat tire).
Be doubly wary of anything from Amazon. Anything to do with mains AC power should be UL-listed (e.g. a responsible testing lab should approve it). Anything you buy at retail (e.g. Home Depot or Target) will meet this standard. Amazon will not. Amazon seems like a legit retailer, but they quietly opened the platform to third party sellers. As a result, it is completely flooded with the same junkstream you see on eBay, but in sheep's clothing: gussied up to look like a legit product.
Products which direct-ship from China, or are drop-shipped from China via Amazon's Fulfillment warehouses (e.g. Prime), do an end-run around all the product safety laws. That may be fine for fidget spinners, but anything that touches mains power can kill you.