You can also try an eccentric bottom bracket. I believe Bushnell makes one for standard BB's now, but I may be mistaken, and it's more expensive than the WI hub.
Don't know about Bushnell, but Forward Components (
http://forwardcomponents.blogspot.co...et-patent.html
) and Triskstuff (
http://trickstuff.de/index.php?p=d116en1
) both have such a beast.