Hey Ali,
The ones from unbeatentracks.com are good
here
The design is good with the large handle for hanging.
Size depends on how many of you there are.
You can of course just use a billy can or one of the zebra billy can kettles.
Enamel is good for a kettle used over a fire as well if you like to be more traditional.
check out
cookshopcom on ebay for zebra billy can and different kettles including enameled ones.
PS - i have no affiliation with either of the links - just have dealt with both and found them to be good!
Hope this helps
Neil