Since nobody else has jumped in yet... I can't speak specifically for your filter, but the pads are most likely being used as mechanical scrubbers (trapping the big chunks of stuff), while the mesh netting could likely be acting as a biological filter (breaking down the waste slowly)?
For mechanical filters, you can get sheets of batting material from a sewing store. It's basically a big white pad of fluff. You don't want to go too thick with this, or it will restrict your water flow. Alternatively, some people use floor buffer pads. These are much coarser material, so it won't trap the really fine stuff, but you also don't have to worry about water flow through it.
For the biological filtration, just about anything will work. It needs to be coarse so the water can flow freely through it, and you want something like plastic that won't break down over time. I have been using the plastic strapping that you bundle boxes with for shipping... just pull a bunch off a spool, wad it up into a big mess, and pack it in place. Some people have also used lava rock, but there is some concern that the sludge from the pond can clog up the little holes in the rock, suffocating your beneficial bacteria. Basically you want to create as much surface area as possible.
There's nothing really special about filter media, except the price that some of these companies charge for it. As long as you understand the purpose of the media you are replacing, there are many solutions that will cost a lot less.
Don't worry, be back and active very soon.