i only heard of Smart Media Card adaptor for xD card. but i think if you want to use your xD as a CF using the adaptor, it will cost more than you sell your xD and get a CF. or you are holding devices using these 2 different storage media?
if you got a CF card reader and just want it to read xD with it, i suggest you get a multi-card reader, it costs little.
Agree with GriGri that a card reader would be a more economical & fleixible solution. But I use a Fujifilm xD-CF adapter because I have an older PC with USB 1.0 ports so I use a firewire CF reader for speed. Bought it almost two years ago at MS Colour for $71. Should be able to find it also at CP & AP