Yes yes and yes!!! I need this. I am have been buying the normal 4in filter socks and cutting them down to fit the Red Sea filter sock tray and it’s getting pretty old.
I don't know if anyone has come up with this but Im currently working on a solution for this. It'll be able to go over the side of a non braced sump, screw into place, connect to your piping (1 inch) and hold a standard 4 inch filter sock. Should be ready by end of week.