I have used old T-shirts and other odds & ends of clothing, leftover bits from my wifes sewing, whatever I had available at times. When we had the gun shop we sold the precut patches and used them in store. After we closed I brought what was left home. Funny thing, once we got in an order from one of the gun cleaning supply companies and they had filled out the box with the punched out sheets they cut their patches out of. The intact sections were big enough to get a lot more patches with a little scissor work!
I also have several boxes of the old patches like some of the other posters show. Somehow, I seem to become a collector of old gun cleaning gear. Hand me downs from estates, from box lots at auctions or just too cheap to pass up at yard sales. Complete cleaning kits and some well used ones, I kind of like having them around and even use some of them. At the last collectors show one of the guys I set up by had a 5 gallon bucket with a lid on it........ Turned out to be full of bags of K-Mart gun cleaning patches from years ago. He offered it to me cheap so now it's with the rest in my workshop. More than a lifetime supply I guess, can supply my kids if they need any!