I made this filter sock plus bracket for the fun of it the other day, I've included some picture of the simple steps it took to make it.
I took a 4" PVC pipe and cut two rings about 1" wide, than I made a 3/4" cut-out on one of the rings for the retaining ring.
I took another 1 1/2" PVC pipe and cut-off a 1 1/2" piece, made a cut through the side for the clamp on the side of the sump, drilled a hole in both pieces of pipes and attached them with a nylon screw.
Next I went to the supermarket and bought .90 cent coffee filter, cut the metal handle off. I saw a bit worried about the quality of the filter so I washed it with RO water, I'm showing the RO water reading 1ppm before the sock was in the water and after with the sock in the RO water for better than 24hr... still 1ppm
That's my filter sock with holder, no need to worry about getting more filters, Sheng Siong Supermarket has tons of them.