Tractor is relatively the easy part as long as the weight is correct to both move and stop the aircraft. The GPU depends on whether you want AC or DC.
There is virtually nothing on the market at present but plenty of used tractors and some GPU's that can be modified to fit. Batteries, for DC only are also a solution.
If Douglas cant help u out, pls come back to
[email protected] as we can probably supply a solution based on used kit modified to meet your need.