You can purchase nathan hydration packs from stores like Walgreens, Walmart and there are other stores that you can purchase the product. You can also ask people who have purchased the product.
Hydration packs are great under certain conditions. If you need both of your hands free this is the viable option. Rather than holding a water bottle in your hand while running.
The British Army use both the canteen and hydration packs
I have heard that CamelBak hydration packs are great to use, but it depends on what exactly you're looking for. Here's a guide to choosing the best hydration pack for you and your lifestyle. http://www.rei.com/expertadvice/articles/hydration+system.html
Yes, I would recommend Camelbak Hydrobak as a great option for hydration packs. I own one myself and use it everytime I travel or go on a long hike or run.
skiing or snow adventure
That depends on where you are, and whether you're talking about water skiing or snow skiing.
I would look at www.runnersworld.com. They have tested the latest in hydration systems, from tiny handheld water bottles to mega over-the-shoulder packs that carry two liters of water and all your gear.
You can try checking out your local sporting good store first. Then you can try checking out amazon.com, or search for well known sproting goods stores like Finish line or lady footlocker.
Heli skiing is done during the winter months because you need snow. Which is why it is called skiing. Exactly when, I do not know. I am not an expert on skiing.
Yes,They did live in packs. Good question.
Cub Scout packs are the bestest ever!