I have Leupold bases with Burris Signature rings on two of my rifles.
Least expensive place I found for the rings is at www.opticsplanet.com
While you're at it, buy the kit with all 3 sizes of inserts (5/10/20) if not two kits. It will save you the hassle of ordering them later when you realize you'd like a size 10 or 20 to align your scope, and all that came with the rings is the size 0.

FYI, both of my rifles with these rings use a 20 size in the front (-20 side down) and a 10 size in the back (-10 side up) in order to line up the crosshairs with my laser boresighter at 100 yards. Doing this I've only had to adjust them 8 clicks for one rifle, 12 for the other to be right on my point of impact.