Most places require a "dead man" return. When you let off the throttle it returns to idle. My 13MM with Ag Gov. returns by itself without any assistance. I used a 1/2 SS rod and threaded both ends to accept a yoke on one end and a Hurst pistol grip on the other. The cable is a morse style cable with bulkhead fittings on both ends and use a ball stud to attach to the throttle lever and pump with a quick disconnect on both ends of the cable. Cable is 4" of travel and mine is setup when at WOT my arm is straight. If you need pics send me a text and I can send you some.
It's been several years but my set up was from ECD and used a quality PTO cable. I imagine they could be had from a good farm supply place or maybe a big truck place. Or maybe just buy it directly from ECD.
Hand throttles can be made really cheap depending on what you have for metal lying around. I made mine for the cost of a 3' pto cable from summit and a weekend. I bolted it right to the bracket for the middle hump suck seat that I took out, I also worked in the idle adjustment to the hand throttle too. I can post pictures if you're interested.
Well I thought about using the button that would be the boom master on a sprayer for the nitrous solenoid.......LOL LOL LOL but no they're not hooked to anything at the moment haha