So far, I've replaced both tires and got them both online:
Dennis Kirk | Metric Bikes Main Page
Had them installed locally for $30 each (rim off the bike), but Cycle Gear will do them for $20 (rim off the bike). Thing is, you have to start looking and order them before you need them. That way shipping is cheaper and you're not stuck with what the dealer has. I would like to go to a CT in the rear next time if I could find one that fits right.