An old thread asked if there were replacement fabrics available for pool skimming nets.
You can order mesh fabric from Jo Ann Fabric and Craft Stores. Follow the menus for Fabric --> Utility --> Specialty. The preferred material is polyester. Here are a couple of appropriate mesh fabrics:
Utility Fabric Cargo Netting (item # 10173359)
Mesh Utility Fabric White (item # 1948439)
Of course, you'll need to sew it yourself into a bag. You'll want polyester thread for that:
Coats & Clark Transparent Polyester Thread-400yds
Hope this helps.