Buy a standard wrist roller if you want, but a homemade version of PVC pipe (1.5 to 2 inches is perfect) with climbing webbing attached is a cheap and amazing solution.
Check our power-rack version that we made out of aluminum tubing. The beauty of it in a rack is that you can truly test the grip without the shoulders giving out first.
Pavel and Chad and bears, oh my! Pavel and Chad and bears, oh my! Okay, there are no bears in this article, but hey, Pavel Tsatsouline and Chad Waterbury working together ought to be exciting enough!