Tin cans and rust

Steve,
I don't know exactly what size you need for your coffee-maker kit, but I think I would consider using an aluminum can/tin. These can be had in a variety of sizes and can be cut to shape with a pair of regular sissors. It would decrease the wt. of your kit, too. Plus- it won't rust.
-Mark

here is a recent thread about aluminum cans.

Most (all?) “tin cans” will rust unless in an arid climate. Some come with an interior coating that seems to be OK for water boiling temps (they get higher temps than that in the canning process). Dinty Moore beef stew cans are that way and are a decent shape. Use a side cut can opener and the top makes a decent lid.

Thanks – I'll have a look around. We don't have Dinty Moore in the UK, but maybe our beef stew cans will be similar.

For an aluminium can, beer cans are too narrow for what I want. They would be very difficult to clean out properly if I cooked noodles and burnt them. Is there a wider, squatter shape to be had somewhere?

I think anything you treat it with is going to be toxic and you probably don't want that in your water/food. It's probably a better idea to find a can w/ similar dimensions of a different material.