What size are the tires? Remember, a fractional size and decimal size may fit completely different rim diameters.
Perhaps you have these...
28 inch (635 mm) Bicycle Tires from Harris Cyclery It looks like Kenda (bless their hearts) sells old 28" sized tires- see the link. I have a set of Kendas on my 63 Schwinn and they are pretty decent.
Or, as Mr. Brown says, it could just be the Canadian name for modern 700C (622mm BSD) size tires which are available at any bike shop.