Your best bet would be to buy any Leica R-mount SLR lens and buy an R-M adapter for the RD-1 and an R-EOS adapter for your 1D. However, this is far from an ideal solution for both cameras.
You won't have rangefinder coupling with the RD-1, but if your lens is wide enough (like a 19mm) and you stop down sufficently there shouldn't be too much of a problem. The adapter isn't easy to come by, and often can cost more than buying an M-mount lens in the first place. There's one on ebay
here.
Furthermore, using an R lens on an EOS camera presents its own can of worms. Metering is only available through stopping down the aperture, and the camera is incapable of doing this on its own. Auto-exposure (except for Aperture Priority) is out of the question. Due to the lens design, autofocus is also an impossibility.
My suggestion would be to just buy two lenses, one in LTM or M mount for the RD-1 and one in EF mount for the 1D. You'll save yourself not only headaches, but also a great deal of money.