When I replace a bandsaw tire, I always replace both unless one is
obviously damage from something like a broken blade.
I don't know anything about the Ottawa area, but these guys have the
best deal I have found on the internet for actual urethane tires.
They are about half the price of others considering they are selling
two tire, not one.
If they are in reasonable condition and not stretched to the point
where they are hanging loose you may wish to try regluing them. You can
use 3M weatherstrip adhesive for this.