Some of the original canvas top rvs used dutch ovens to bake recipies on
their vacation travels from Missou to Oregon and California.  Pizza can be
made just dandy in such a dutch.  There is a Yahoo group on
dutchovencooking.

The basics are that you need a hot air container that can maintain the
'pizza' environment for long enough to cook pizza.  The Coleman folder
almost fits the westy stove to a 'T' and is perfectly serviceable for pizza.
It is a simple flow through device with a heat retention plate.

But looking at teh (sp) problem from another aspect, a simple hot air stove
can be made using two nesting metal cookie containers such as the ones
shortbread comes in.  Using a deep container with a lid as the enclosure and
three large hex nuts as a support inside, a pie tin or similar metal dish
can be used to heat contents to the desired temperature.  Use a magnetic
outdoor BBQ thermometer to monitor the surface temperature of the outer
cookie tin.  Takes a bit of practice but can be done.

A cast iron dutch oven is more versatile and fits well under the seat.

Using a cast iron circular griddle as a heating plate and a suitable
container on the plate is another approach.

To properly operate a 'toaster' oven you'll need one of them gem-dandy Honda
2000i portable generators.

Decent used Griswold CDOs can be had for <100USD or you can buy a lodge or
tex-sport for less gelt.