Bontrager cages are sold at Trek dealers. You can buy them on line but they cost the same as the store but you have to pay for shipping as well. If you have a Trek dealer they can get it for you minus shipping charges. If not you can try this place: Bontrager Race Lite Bottle Cage | Evans Cycles but they will charge a $12.65 delivery charge.

Also Polar bottles are relatively inexpensive and thus the prices are the virtually the same in an LBS as it is online after shipping charges. With the Polar bottles the ones that are the lightest in color are more efficient at staying cooler, like the all white one or the platinum one.