You could buy 1x1, 1x2, or whatever size wire at any hardware store, maybe feed store, and fasten it with hogrings or the clips for building rabbit cages. Very easy to make it however you want it.
The one I use now came from Memphis Net & Twine,it has a draw string top I float mine with a pool noodle around the top hoop so as you catch you can drop the catfish in.
^^ These work well. Can buy them or make them. I will be making one very soon.