The Kenwood KCA-R6A can be found easily online through google, for instance here

It doesn't have all the features of the Rio remote (all longpress options etc), but it's the closest thing to the real deal - used to come with the MkI (and IIRC with the MkII).
Differences can be checked out in the Button Guide, and here

Edit: Regarding the sled - your fastest, simplest and cheapest option is probably to find someone local to you that knows how to solder - the harness is not very hard to work on (compared to some of the internall SMD stuff...). Info on how it is wired can be found here and here.

/Michael