Huzzah! John Townsend to the rescue, once again. In an earlier post, I described period correct canteens, along with leather covered glass bottles, as period correct ways to slake one's thirst while on a trek. This video popped up in a search of the Townsend channel, and I wish I had seen it earlier. It was originally posted in 2010, so it has been around for some time.
Costrels are an alternative to the traditional canteen. This video provides some suggestions on how to maintain your costrel, or any other form of leather canteen.
Note: I checked the Townsend on-line catalog, and found that the costrel is no longer sold.
Make Your Own Canteen: If you want to really live the life, you can make your own canteen using vegetable tanned leather. This Townsend sponsored video gives you a step-by-step account on how it is done.
Brewer's Pitch: Boy, those Townsends think of everything. Here is a primer on how to waterproof a wooden or leather canteen. If you buy a tin canteen, you may need to periodically re-pitch them to keep them waterproof.