Most art supply stores sell Silk screen material, either loose or mounted in frames.
In a frame they make pretty good dry-sieved hash - done it a few times.
I haven't done it, but I don't see why one couldn't sew the same silk screen at the bottom of a nylon bag / tube and come up with a DIY Bubble bag. If you have a screen printing suppy store in the area, I'm sure you can find several different screen sizes. Sure you could find the material online as well.
Hmmmm, Perhaps I have new project....