I know, I know, I'd never buy one but this one arrived from a neighbor!

The outlet copper tube is held in place and sealed by a small rubber
gasket, looks like an 'O' ring with a molded on flat spot on one side.
All of this sets into a grove in the cast aluminum (??) head. Head gets
hot, vulcanizes the rubber, rubber gets hard, tube gets spit out of the
head. New gasket is $2.16 plus S&H, no delivery date, not available
locally.

Proper fix is to drill and tap for a 5/16" compression or flare fitting,
not enough thickness to get a realiable thread. Plus I'd still have to
seal up the old slot. JB Weld to goop in proper fitting has some merit
but that brings up a few questions:
1) Would it hold up to the heat?
2) Would it hold up to the vibrations/pressure?
3) Is there something better than JB Weld for this??

Worst case is I order the gasket, install, and send it back with an "I
don't want to see this again"