If I recall correctly the original box had ring connectors on the power and motor feeds, the newer units have spade connectors. I simply chopped the original connectors off then crimped, soldered and insulated the new connectors (using heat shrink tubing) Probably take a couple of hours max to do the wireless conversion though while I was at it I also moved the control box from the gas locker to a more electronics friendly position close to the battery locker, tucked away under one of the beds.
There are single axle SOFT START REMOTE CONTROL UNITS on ebay at the moment item number 360171547819 - I have no connection with this seller though it may be where my box came from as the name looks familiar.