I order mine from Eco Bags. The ones I use are made of organic cotton and they're pretty cheap. I like them because you can put the herbal tinctures in them and pull the draw string closed and then press away.
I first bought the medium Consiglio press because they were out of stock on the large one. Just recently I bought the large one when it came back in stock so I've got to order some large bags.
Thanks for reminding me, think I'll go do that right now lol!