--snip--
> I'd like to line the inside lid of the
> 'q with stone lining, but I can't picture what kind of adhesive could be
> used that would not outgas something horrible, would hold up the vehicle
> vibrations and the heat of the fire, and accomodate the different
> thermal expansion coefficients of the metal and stone.
--snip--

Plant pot... y'know, those orange-y things with the hole in the bottom. Find
a heavy one of the right size (diameter/depth), invert it over the pizza
stone (presumably with the pizza or whatever in place first). Get a
replacement grill thermometer at HD or someplace similar, same place you get
the pot (the one I got goes up to 700 F), drop it in the hole, and there ya
go.
The hole also helps you pick up the pot, if you have an appropriate
implement or asbestos hands; serves as a smoke hole if you decide to smoke
something (or if you're a lousy cook and you burn your food).
It won't even cut into your '100 pounds' much. : )
When you're on the road or storing it wrap it in and old towel and keep it
in the grill.

Cya,
Robert