I would pick a grade of canvas or heavy cotton that seems to be suitable for the item you want to make then coat it. I think the various tin cloth items sold vary a bit around the base fabric.
Here is what Filson states about theirs:
Filson Tin Cloth
The toughness of legends -- 100% Cotton Tin Cloth in Oil or Dry Finish.
When customers try to describe just how tough our Cotton Tin Cloth is, claims of "it actually saved my life" or "I've worn it for 50 years" aren't uncommon. It earned the name Tin Cloth decades ago when tin was the standard for toughness. Incredibly heavy and rugged, it's still the fabric of choice for maximum protection against rain, wind, brush and abrasion. 12.5 oz. oil Finish Tin Cloth is the most durable, abrasion and wind resistant cloth we make
To create the Oil Finish, our heavy, densely-woven cotton Tin Cloth is completely soaked in a paraffin-based wax. The highly water repellent finished fabric (12.5 oz. per yard), although very stiff at first, softens with use, gaining character over the years. Not designed for machine washing or dry cleaning. Clean by wiping or brushing only -- gains character with use.
They also offer a lighter weight material soaked in the same oil finish...Shelter cloth:
Filson's Shelter Cloth
A lighter weight alternative to our Tin Cloth -- 100% Cotton in Oil or Dry Finish
Shelter Cloth is both softer and more pliable than our Tin Cloth. Yet it's surprisingly strong. Named after military shelter tents, this dense fabric is made of high-quality, two-ply cotton yarns tightly woven in both directions for added strength. Although we call this cloth 'mid weight', many would call it 'heavy-weight'. 8.5 oz. Oil Finish Shelter Cloth: when maximum protection against rain and wind is your top priority
The perfect combination of fabric and finish for the outdoorsman who operates in very wet conditions. Comfortable Shelter Cloth is treated with our famous paraffin-based wax. The result is a garment that is extremely water repellent and wind resistant, requires no break-in period and is comfortable the first time you wear it. Not designed for machine washing or dry cleaning. Like our Oil Finish Tin Cloth, it can be cleaned only by wiping or brushing it off, and gains character with use.
This is much tighter weave, and thinner making it more flexible and in my view more windproof. Most of the Barbour jackets I have seen are like Shelter cloth not tin cloth.