That's what I need to do and find a way to make extra cups. The one I have those cups are $18 each. And there's not much to them.
Making the cups is easy.
For a simple cup here is how I make mine.
First cut your PVC pipe to length. You can use 2" or 3" pipe depending on what you want.
Then insert a knock out test cap in your PVC. These caps are available from your hardware store where you got the PVC from for ~.35 cents each.
Place the PVC on a hard surface and knock out the center of the test cap with a hammer and discard the center piece.
Next remove the remaining ring from the knock out test cap. Place your filter membrane over your PVC cup and replace the ring for a nice tight fit and trim the excess filter material. You now have a fluid bed cup.
For the filter membrane you can use all sorts of stuff. Printer paper of different weights,Brown paper bags, Tyvek house wrap (label side up) or get Tyvek free from the post office envelopes. The outer bag material from vaccum cleaner bags, coffee filters etc. etc. Each paint with it's different pigments may prefer a different filter membrane.
For hard sided cups I bought some Fluidizing plate from a guy on EBAY, I used a drill press and a hole saw with the centering bit removed. I cut them to the approximate size then had to sand them down a hair to fit my 2" cups.
Then glue them in with a hot glue gun. I got the 8"X8" fluidizing plate for cheap enough(can't remember offhand how much) and I made 9 circles for my 2" cups from one sheet.