(i know this topic has sat for a while, but, as mentioned above, menstruation is under-discussed. so here's my few cents)
here's a post i wrote about dealing with my moon times in the alaskan interior: feralforest.com post about rustic menstruation. there's a photo in there of a tri-fold pad i made (back when i had a treadle sewing machine, though they're easily doable by hand) out of an old flannel bedsheet. i made a few of them, and they're sewn so that i can stuff them with absorbent material to thicken them up. they're already made with two layers of flannel, though, and then folded over into three layers, so they do a pretty good job already. i just use a safety pin to affix them to my underwear (which i only wear during moon time).
i don't have any brilliant suggestions about things to actually insert, though. i only use a menstrual cup, since i got toxic shock syndrome about a decade ago from leaving a tampon in too long. will never use them again. i don't like the mess of pads, but they're the only thing i've got if i get rid of the mass-produced menstrual cup.
if you live near the ocean, maybe you can actually harvest sea sponges? i have no idea what that process is like, but i do know they were popular for menstrual use for a while there.
i wouldn't expect usnea lichen to be very absorbent, based on how it feels to me personally, but spaghnum moss would be a different story, and it's also anti-microbial, etc. though i'd maybe tuck it into some kind of cinch-able mesh pouch, so i wasn't worrying about getting bits of moss out of my vagina. good luck, friend. speak boldly about your crotch, and eventually others will follow