We've used a metal garbage can lid as a firepan for years...
BLM on the Rogue allows them, but not sure about other rivers. Some weeks (during fire season) you aren't allowed to have a fire anyway, but if you need one, the garbage can lid is good to go!
Hope this helps.
+1 on the snowmobile trailer, that's what I use.
"Good judgment comes from experience, and a lot of that comes from bad judgment." ~ Will Rogers