I don't know where you live but there are plenty of nets to choose from... if you look into diving and spearfishing gear stores. We (I spearfish) use them for carryng wet gear or gathering shells, abalones (where allowed), crabs of any kind (again, were allowed) etc.
Check this out. I am pretty sure that this site/store has also its own US equivalent:
https://www.scubastore.com/buceo-submarinismo/bolsas-y-cajas-bolsas-de-red/61/s
The ones with rigid handles are very handy, because they kind of solve the problem of the net closing by itself once you put any weight in it.
I hope it helps!