I bet Hillman's on Dickinson bayou can point you in the right direction.
I shrimped for about ten yrs. back in the late 70's and early 80's, and I've helped several people rig out sportsman nets through the yrs. I personally wouldn't mess with one today, because of the hassle. If your trying to use it to catch bait, your gonna lose a lot of time in the mourning dragging the net. You have to store it on your boat while your fishing and that means it's probobly gonna be in your way. Your gonna beat your boat up hauling it in and out, and you have to have a tub or something to "cull" your catch in. If your thinking that you can catch table shrimp with the little net, think about the price of gas these days. It's cheaper to buy the shrimp.
If you really want to mess with the net let me offer one more idea. Get a 12' or 14' "try net", because you can only use doors that are 15 x30 " or 450 sq. inches with a sport net, and they will not properly open a twenty foot net. The smaller net will "fish" better than a bigger net thats going through the water like a horseshoe. The small net wont take as much gas to pull either. good luck