I've used two generic relays to control the motor on my SPX. This requires quite a bit of wiring wizardry and trial/error, but if you want more details, I can explain how I did it. You need a basic knowledge of how a relay works and a test light. I housed this in the grey box next to the mpem. Worked well, just had to look behind me to judge where the trim was. Now that I think about it, I COULD have left the trim sensor hooked up. But being young and dumb, I just cut all the wires to the whole unit and ran two wires only to the motor.
Easy way though is to just get one from Westside Powersports