I remember back in the mid-90’s, running against a guy who had a VERY LARGE friend who push started him. Not to sound mean, but the friend was of a shape and size that he couldn’t bend down to push start him. The tool they used? A hockey stick, with the blade cut off and the end of the shaft of the stick cut into a “V” groove. He could basically stand in one spot or maybe take one or two steps in an upright position at a normal walking pace and give a push and the thing would fire up.
The point being, you don’t need anything fancy. You don’t really need much speed or distance to start a shifter, so anything to just get the thing moving will usually do.
I used to run direct drives against some guys who used the 5th wheel that Walt mentioned. I never saw then used on shifters though – not that they couldn’t be – I just think they might be more suited to direct drive that normally takes more speed and space to get going.