I've recently started putting a backpack on my Aussie puppy. It's an REI brand with a chest strap and two belly bands. She wears it without a fuss, and I load a water bottle on each side to balance the load. I'll gradually add more to the packs as she gets older. I've been very pleased with the back pack. When she outgrows this one, I'll probably get one of the backpacks that has removable packs - I forget the brand name, but Cabela's carries them. If your friend intends to do much hiking in the hills/mountains, the type/brand will make a difference. Some brands will slip down over the dog's head going downhill - they learn to slip out of them on the downhill. Seems like I Googled dog backpacks and found some good reviews about the pros and cons of various brands.

I have an old pack I made years ago for my first dog. One of my current dogs used it last summer on a backpacking trip and she did fine with it. It initially fastened just with velcro, but that wasn't sturdy enough, so I added fastex quick release fasteners. Even if the pack is waterproof, make sure you put the dog food in zip lock bags, especially for breeds that like to go in water!

Wildchild - Thanks for the info on ziploc baggies. btb - He's at his full weight of 70 lbs.