I cut up a sheepskin noseband that I got from my local tack shop, but it would probably be cheaper to go to somewhere like Dunelm or another fabric shop and get a big piece of fleecey material.
I got some cheap sheepskin nosebands from America but on ebay they do sell sheepskin nosebands especially for muzzles. I thought I had made a fantastic discovery when I adapted a sheepskin noseband myself some weeks ago and put it on the forum for others to see. Natural is best rather than synthetic as it breathes and doesn't get so soggy in the rain. My horse got a nose splint thanks to over zealous foraging with her greenguard on last year and looked like a rhino, fortunately it went down after a year BUT I was not prepared to take the chance again. Good luck!