Hi:
Bailey has 2 backpacks, one is specifically for her SD work, it's the larger of the two packs and carries all her basic need items (portable water dish, disposable bags & wipes, emerg. items, id, etc. It was purchased through Wolfpacks SD Equip. It's very durable, fits her well and has lambs wool covering specific areas to prevent rubbing, etc ... it was also very expensive!
Her other pack we purchased at Petsmart from their selection of apparel made by Outward Bound. It's also an excellent pack, it's smaller than her working pack ( that was intentional ) and doesn't hold as much ... but we really only wanted it for keeping the bare essentials in when we're out during leisure time, she's not working. It's also very durable and fits well. It wasn't nearly as expensive as her working pack ... actually if we ever have to replace her working pack we just may go with the larger pack for Bailey's size that Outward Bound makes ... other than the protection for rubbbing there really doesn't seem to be that much difference ... and I can put her patches on it myself.
We like to use the packs when out with her because we're really not able to walk at a pace fast enough to wear her out and give her the exercise she needs ... the added weight of the pack helps out in that respect.
Take care: Hivin