Wheels Mfg is a good solution. They basically put corrected spacers in an ultegra (or DA) cassette and provide spacers for you to tune where the cassette comes up agains the hub body on the inside. Works well, i have one.
With a little more money you can get a Ti Cycle dynamics. Lighter and more custom choices on gearing.http://www.bigtwincycling.com/cycle_dyn.htm
Hm, i only see Campy->Shimano conversion sets there, not the other way around. Am i blind?
I, too, like my Wheels Mfg 10-speed Casette, btw. Lighter than the AM Classic
Snowman and Strong Walker
my old stuff
my new stuff