I've been looking to find a cheaper source of good floats and think I have - Suzuki floats. Suzuki used very similar Mikuni CV carbs on some of their bikes in the '70s and '80s. This one for the GT750 and GS400/425/450 appears to be the Yamaha BS38 equivalent .....
http://www.partzilla.com/parts/detail/suzuki/SP-13252-31210.html
At about $27, it's quite a savings over the near $39 Yamaha one. I happen to have a set of GS425 carbs in my junk carb box and their floats do match the 650 BS38 ones.