You can use cotton butcher string instead.
Long before the bore snake ever became available on the retail market I would make something similar out of cotton butcher string. I had a two by four with 2 finishing nails on it about 3 feet apart. I would simply wind cotton butcher string around the 2 nails as many times as I needed to get a good snug fit in the barrel of each caliber I had. The number of loops depends on the size of the cotton butcher string you buy.
Once the correct number of strands were wound, I would just loosely braid the loops so it wouldnt tangle up and tie off each end. If you dont know how to braid, just ask your wife for help. I then tied a single strand of heavy nylon fishing string to act as the pull through with a small fishing sinker on it to drop through the barrel and get it started.
I kept the string in an old largemouth bottle of Hoppes or ziploc bag and added a bit more copper solvent on it to freshen it up before I would use it.
It was great, because it went all the way through the barrel and once pulled in, I would just leave it soak (making contact from one end to the other) for a while and every now and then tug it back and fourth a bit just to help it get into the nooks and crannies.
I later made some with a piece of fine scotch bright (kind of like pot scrubber side of sponge) at the tip where I tied the nylon fishing string to the cotton and that worked even better. I had some that were soaked in solvent, some that were clean and some that were oiled. In my opinion this works better than a boresnake anyway.
Who knows??? maybe that is how the boresnake guys got the idea in the first place... never know, maybe I showed one guy too many.