The closure mechanism on this crossbody bag is a zipper. This crossbody bag is made exclusively from nylon and it holds 0.8 litre.
From Amazon
FJALLRAVEN Unisex High Coast Pocket Shoulder bag, Black, 0.8 L UK
The product is available from £34.15 at international stores.
Trekkinn
Fjällräven High Coast Pocket Crossbody Black