Hi Jo,
You can use any deep pan with a long handle and a cover that can be used over a fire. Have a good oven mitt handy and a helper to take over if your arm gets tired because you'll have to keep that pan moving! Here is a recipe for you that will work for an electric popper, on the stove or over an open fire:
How to Pop CornAnd here are a few pans available made for popping corn over a grill or fire:
Campfire Whirly PopperCoghlan's Corn PopperGrill Popcorn PopperUniflame Popcorn PopperHappy Cooking!
Betsy