I am in Winnipeg and we have at least four specialty stores that carry small band sizes. At least down to 30 but a few also have 28s. Some bras fit smaller than others too. If you check the yellow pages or google for lingerie stores in your city, I suspect you will find a few. Just look for ones that carry lejaby, prima donna, freya, fantasie, panache, etc. Those are the brands many of the better shops carry.
Most of the experts suggest a snug fit on the loosest hook and say you will move to the next hook every 3-4 months as the elastic starts to wear out. A year is the max life for most bras unless you have a lot for rotation.
I usually have too many but wear the same 3 or 4 most of the time.