Leica-M to Nikon AND Nikon to Leica-M Adapters???

Does anyone know of/can anyone recommend one?? If you have one or have used one, what's your thoughts on it?
Many thanks,
Paul

Oh wow, I've just seen this:

http://www.cameraquest.com/adpSLRRF.htm

Seems all I need to do it find a viewfinder, then I can use my MF 20mm Nikon on the Leica!!!

Please, do reserve your comments about why I would ever want to use a Nikon lens on a Leica. I've heard all that before. I have both Nikon and Leica gear, and all I'm really looking for with a device like this is the chance to mix & match some of the gear. I mean, I can't afford a Leica 21mm at the moment, yet there's a great Nikon 20mm sitting there. I often have to take both kinds of gear out because one system has something the other doesn't. Anyway, I'm rambling now....