In my experience you're going to pay about the same for a lock anywhere you go. I'd choose to support a place that's local and supports the community. City Bikes, as already mentioned is a sweet co-op. On the other side of town, the Community Cycling Center (on Alberta) turns your money into classes and bikes to teach young disadvantaged kids to be bike commuters. In this town there is no reason to support the chain stores for accessories (bikes themselves are another issue, IMO).