If we were to, I think fuel or electricity should be ideal, as both can be produced relatively easily. Perhaps it could run on the same fuel as the stack, or at least a fuel with similar components. If we will be mining fuel for that, we may as well divert a bit and use it for the rovers.
An internal combustion engine with LOX/LH2 as fuel? :lol: or wait, fuel cells?
Electricity will be in abundance because of the nuclear power plant. I guess its a matter of which is more reliable for its weight.