Supermarkets don't stock it. Most quilt shops do - but it is about $17.95 for a box. It is 16 2/3 yards x 18". I bought a box over 10 years ago and I still haven't used half the roll.
Expensive, but it lasts a L-O-N-G time.
Butchers over here - if they use paper at all - use butchers paper - like the paper you get in kids cheap scrapbooks. Most use plastic bags.