I looked along time before I found a USA supplier of custom landing net bags. I wanted a soft nylon net bag with gently curved bottom, so not to over bend the spine of a fish you wish to release and cause unintended injury. These bags are made of a soft nylon with a fine mesh to avoid fin injury. They are made in the USA, each net net is hand cut and sewn so there is a degree of variation, this is particularly noticeable in the smaller sizes. The soft mesh is very consistent but the exact shape of the bag varies with both size and the manufacturing variation.
To select the correct size of net bag for your net, measure the circumference of your landing nets hoop (as pictured). I have found that the shape of the hoop can effect the fit of the net bag. I suggest ordering the next size up for a round hoop shape.
32-33 inch circumference - 11 inches deep
34 inch circumference - 11 inches deep
36 inch circumference - 11 inches deep
38 inch circumference - 10 inches deep
42 inch circumference - 16 inches deep
45 inch circumference - 18 inches deep
50 inch circumference - 20 inches deep
60 inch circumference - 22 inches deep
70-74 inch circumference - 20 inches deep ( these have a fairly shallow curve so they have a cradle like shape.)
The net bags maybe selected by scrolling through size choices. Priced starting $14.00.