Where can I buy the square cooking pots used by Doug?
If you cannot find the exact Coleman pan, you may consider
others below.
Smaller ones can be found in mess kits at Military Surplus
Stores. I think that more than one country used rectangular
pans.
If you want bigger pans, I have seen squarish pans in
stainless steel sold commercially; 9 by 9 inch was very handy
for me. It was sauce or casserole pan that came with a
tupperware-type snap-on lid and no handles.
For words to consider for searching:
roasting casserole oven "folding handle"
Good luck on your hunt.