Plenty of used lithium batteries in junkyards from hybrids ready to repurpose.
Netgain motors are not expensive.
Need a controller, charger and probably can repurpose the radiator for battery cooling. Wire the batteries to the controller, wire up the motors. It's all pretty simple. Some fab work for a new cross member to hold the motors and brackets for the batteries.
I priced it out less than $10k...puts it within the cost range of a lot of swaps.
-Mac
But you'll look funny with your red rotopax's