The CAP for the Frig. Burner Drain, the male cap (plug) that screws into the
drain tube exiting under the frig., is as I recall, a 7mm X 1.0 metric
parallel thread. In general, 7mm is not a common stocked size.
What I am about to suggest next is really OFF THE WALL but....... The bolts
that fix the rear brake drums to the rear hubs are 7mm. Sooooo, in a pinch,
one could "barrow" one off either of the rear Drums. Fit an appropriate
Sealing Washer and you would be good to go! I admit my suggestion is no easy
fix. If a Plastic Tire Valve Cap fits and seals with a modicum of
reliability..... sounds like a more realistic solution. As for a Source for
a replacement part? Check the N. Amer. Distributor for Domestic. Recall the
West Coast Office is just outside of Portland, Oregon.

I too am at a loss for finding a Source for the Fresh Water Tank Cap
(meaning DRAIN or FILL???). I believe the Fresh H2O Tank Drain Caps are
available from a few of the list venders as for the Fill Caps........ I
believe either an Auto Wrecker or a New Complete Fill Assembly (major$$$)
are viable options.
Good searching to you. PZ