Hi Dave,
Here you go:
VideoGear.co.uk - Canon XL to Nikon Lens Adapter
Works a treat. There are a few things to be aware of:
First is that you get a "lens" warning flash red in the viewfinder while using it, but you soon get used to it.
Secondly, it only works with Nikon lenses with an aperture ring, NOT the newer G type lenses.
Also, as you probably realise, you can only focus and zoom manually using the lens controls and you might need to add screw-in or square mattebox/cokin type ND filters to the lens you use as the ND filters on the XL2 are on the lens not in the body.
Cheers,
Rog