One f the members of the club I go to makes them, think they cost a fiver, so not bothered to do my own.
I picked up a couple of packs of 100 .22 rimmy patches of the bay - which, as I shoot .177 mainly and I'll cut them in half - will last a few years, think that they cost about a fiver for the two including postage (it was 'free'), other than that, cut up 'J cloths' make good ones.