So, as my Grandma Martha would have done, I made my own. I will not pretend to have a plastics recycling and processing center in the back of my bathroom closet, but I do have cardboard that comes in from all manner of purchases and was just itching to be turned into mini-bolts. I started with 5" x 10" chunks of cardboard, then cut 1" x 2" tabs in the middle, one inch from the edge:
My storage rule is only using at least 1/2 yard for the cardboard bolts, which isn't that hard since I'm one of those annoying stash-slashers, and folded twice lengthwise - so the selvedges meet and then in half again - they hook onto the cardboard like this:
All folded up, they look like this, stacked up with their big sister bolts: The 10" height ones also fit just right on several of my bookshelf levels standing upright, so I won't have to worry about them getting lost at the bottom of a bin any more. One day I may well upgrade to the longer lasting plastic ones, but for the time being I'm happy with the quick little storage project that keeps my fabric tidy, un-lumpy, and clean.