Canvases are an in-game resource in Paradise Cove. They can not be bought but can be acquired through sending ships on voyages or collecting from merchants.

Canvases are used in the crafting process.

You can gain canvases from

Merchants Tier Ships Tier
Soap Maker Cpt. John's Merchantman
Weaver Crafted Cruiser
Parchment Craftsman Cpt. Phillip's Frigate
Wool Blanket Merchant
Dress Maker
Linen Artisan
Glass Bead Blower
Kangaroo Ranch