when I can't get out to London to buy Arva Flour, I go here, Grain Process Enterprises
115 Commander Boulevard
Scarborough, ON M1S 3M7
They aren't open late and I didn't get a chance to even call as there isn't always someone answering but they do have spelt flour (white and whole in large bags) but I didn't look for the high gluten flour. But I believe you will find it there. They also had organic unbleached wheat too.
The Loblaws on St. Clair between Spadina and Bathurst (Forest Hill Market) has a large organic section with a wide variety of flours. I don't do well with gluten, so I tend to go for flours in the other direction, but they do have many different organic flours there. I am not sure of the other Loblaws in Toronto have the same variety, I have only shopped at that one and it is quite large.
Gluten flour is available in all the Bulk Barns. Just add a little to your regular or All Purpose.
High gluten flours are available from Arva Flours in London, Ont., they will ship, and from Robin Hood Best For Bread. You can figure out the protein content from the white nutrition label.
There is generally a strong correlation between protein content and gluten levels.
The exception is spelt flour, high in protein (17%) and low in gluten, and difficult to rise.
If you buy gluten flour at Bulk Barn, or elsewhere, it will be expensive, and very high in protein, close to 20%. But you only need to add a little bit to All-purpose flour for good risings.
Thuet uses Arva Flourmills, London, Ont.
J. Kennedy uses a red fife source near Peterborough. It is pricey compared to Arva.
Some amateur bakers use King Arthur Flour, Vermont, but there are cross border problems and reports of poor packaging.
Frankly, you can make superb loaves at low cost with R.H. Best for Bread, or R.H. 7 grain, or Rogers rye, all available at Highland Farms, all unbleached.
I use Ruhlman's Ratio as a recipe guide, and a simple Starfrit digital scale, since volume measurements are not at all helpful, just misleading.