This is a Louis Vuitton Pochette accessoires (M40712) of Louis Vuitton.

LOUIS VUITTON HANDBAG POUCH ACCESSORIES NM CANVAS MONOGRAM M40712

I've seen people using the Pochette Accessories with a chain strap

Louis Vuitton Pochette Accessoires - Monogram Canvas - Depop

The multi pochette accessoires is a hybrid cross-body bag with multiple pockets and compartments that brings together a pochette accessoires, a mini pochette accessoires and a round coin purse. Fashioned from monogram canvas with a mini monogram pattern on the sides of the two pochettes, it has both a removable gold-tone chain and an adjustable inscribed jacquard strap for multiple carrying options.