As teenagers, we used to get ours from the outer Cobb in Lyme Regis.
We used a 2m ring of mild steel rod (the concrete reinforcement type) with a muslin sheet across it. In the middle we'd tie a mackerel, with its guts hanging out. Left in the water for an hour, we'd get plenty enough to sell to the local fishmonger.
We stopped netting them after we found a dead woman floating in the sea. We were very adult about it. We tied a leg off on our painter and rowed the body back to the Cobb. It all fell apart when a local fisherman arrived with a bucket and shook the shrimps out of her skull!
You might try an adaptation of the creel. We started a system, which still flourishes in Lyme Regis today, some 50 years later. We made our own creels with defunct orange boxes and scrounged offcuts of chicken netting. The weights were a couple of bricks cemented in the bottom and the floats and lines were the results of our beach combing. You always get loadsa shrimps where you find crabs and lobsters.
All you need to do is to line the creel with muslin cloth, to catch the little jiggers
Now. If you make the trap entry very small, say just 1/2" across...... and maybe use several in the creel, then you will not get any large visitors. Bait it up with ripe fish guts and away you go!
Just check that you do not need a license for the creel!