Russ, there is a lighter, stronger one. GKN motorsport MS3K031
It's honed, undersized balls and a lot of metal machined off the outside. search for the part number in this catalogue.
http://www.gknservice.com/fileadmin/user_upload/Brochures/English/Motorsport_Catalogue.pdfthere are stronger ones again but they use a different spline count or bigger bolts eg MS3K038 or MS3K037
when I bought mine they were 110GBP each
how much stronger they are, I can't answer but they were very good people to deal with.