:Bump:
I too am in the same dilemma. I got a new bullhorn handle bar for xmas, been riding brake less for awhile now, lookin to get a single lever to fit on the 26mm bulge next to my stem. I bought a pair of of Sunlite levers that said 26, but after failing to mount them i'm back in the hunt.
I thought about getting some 31.8mm levers and using shims, anyone ever try that?