I suppose one option is to record yourself playing the piano reduction of the orchestral part. Never tried it myself, so not sure how well it would work.
You could get a friend to learn the reduction and rehearse it with him/her.
to me this seems like the only logical way to proceed. Recording the part yourself or playing along with Music Minus One simply doesn't work...I have tried it with Rach 2 and one or two Mozarts and you just can't keep in time with a recording. There has to be someone actually there to vary the pace and keep in time with you rather than you keeping in time with it.
Surely someone of your stature has lots of orchestras at your disposal whenever you feel like practicing a concerto?