Either Caldwell or Harris. Buy the Harris if you can afford it, if not, get the Caldwell. Which ever one you buy, get the canting model with the leg notches (save yourself some headaches the first time); and get a pod-lock (they make them for both). Len has the bipod locks available here, or Alpha-Bravo has a couple of different versions on MidwayUSA. Make sure the bipod lock is for the brand bipod you buy though.
Good luck.