I also carry several sharkbite assorted fittings and half dozen 3 ft lengths of pex for emergencies. All the lines in our Lexi that I've been able to access are 1/2 inch, so I imagine your rig is the same.
Assortment of O rings, roll of teflon tape, some rubber O-type rings for fresh water hose are also good to carry
Also, get a small tubing cutter, one of the small type thats easy to get into small areas. Invalueable little tool, and necessary to get a clean edge end when working with pex.