When you find the power and ground wires for the WW pump, check to make sure you have power when the WW is turned on. If so, should be no problem getting a tank/pump from your auto parts supplier, as long as they have one that will fit in some place.
Even if you have to extend the wires and hose, it will be much cheaper than going the OEM route.
Happy Glamping, Norman & Elna. 2008 Winnebago Adventurer 38J, W24, dozens of small thirsty ponies. Retired after 40 years wrenching on trucks! 2010 Ford Ranger toad with bicycles or KLR 650 in the back. Easy to spot an RVer, they always walk around with a screwdriver or wrench in one hand!