"backpack from" is correct and usable in written English.
You can use it to indicate the origin or source of a backpack. For example: "I bought a new backpack from REI."
Denby removed his battered green backpack from the couch.
Time to re-up with his pannier-like backpack from the US bag champions.
One boy discreetly drops a backpack from a third-floor balcony to his friend below.
Afterward, retrieving my backpack, from which an important file had gone missing, I thought, O.K. airlines, I surrender.
When Leigh Anne told him to get his backpack from the foyer, he had no idea where that was.
Take the ball to school in a cheerfully cute, themed backpack from Sportpax, which does football and rugby variations.
Half a century after western hippies began backpacking from Europe to Asia on the old Silk Road, young Chinese backpackers are discovering the joys of hitting the road.
Nearly 5,000 backpacks from a school supplies company.
At one point, the informer retrieves two backpacks from the trunk.
Among the glaciers along the mid-Alpine ridge between Italy and Austria, they tote their backpacks from one mountain lodge to another.
Wandering with our backpacks from one residential street to another, we saw no signs of public transportation.
