I make similar traps for a hobby sometimes and have great luck with exactly what you started out with. I run an occasionally crawfish trap too and use the same baits with a little meat or fish.
I will use whatever is handy, stale bread, saltine crackers and occasionally range cubes in the bait box. There is a feed store near my shop and I pick up a large bag of range cubes once a year and will bait a hole for catfish with them, my crawfish traps and sometime my bream traps.
I honestly don't know if the catfish are attracted to the range cubes or the sunfish they draw, but either way, they are cheap, easy to keep for long periods of time and seem to work really well. They do attract rats also you need to store them in something airtight between trips.