Most decent garden centres places where you buy plants will have it. If you can buy some mycorrhizal fungi inoculant too and use it when you plant that always good practice for most plants especially woody plants that last longer than a season (perennials). Blueberries unfortunately need a slight different version (ericoid mycorrhizal fungi) for optimum health so you might want to see if its worth the extra cost as only a small range of plants need this type.

Also if you mulch it with wood chip either put down some carboard with holes in it to shade out the grass or remove it. Mulch heavily at least 2-3 inches and if its been dry near you soak the ground first.