Are you sure you don't already have one? What year XLR? Most of them are coming from the factory with one installed already.
Now, the valve on it may be installed backwards from the factory, but that's another thread...
If you don't have one installed, you can buy one from your dealer, Amazon, Camping World, or eBay. It's usually just a matter of finding your water pump, disconnecting the hose from the inlet side (toward the FW tank,) and placing the T valve and hose on there, and reconnecting the inlet hose to the T. Good luck!
2015 XLR Hyperlite 30HFS5 (mods being performed regularly)
2009 Salem LA 292fkds (gone)
Nights- ('12)23 ('13)23 ('14)15 ('15)31 ('16)25
2014 Harley Davidson FLHX (XLR cargo)
2014 VW Jetta TDI (diesel sipper, camping support vehicle)
2011 Ram 2500 CC 4X4 CTD, B&W Companion (toy hauler hauler)