Here is where I order my netting and all other net supplies.  http://www.memphisnet.net/

I use mono for frame nets. If you want to go cheap you can make the frame out of 3/4" pvc (schedule 40) and use rebar to weight the bottom and crab trap floats of 8" diameter for the floats. I use 5/16 stainless steel rod and make a round hoop 5' in diameter. This equals a little less than 16' perimeter. I use one 4 pound weight when the current is normal and a second on when it is strong. (I use dive weights)

Best regards,
Sebastian