Exactly what Toby said. The Cow Town rubs are also nice and Head Country is a good all rounder. Head Country sauce is also nice.
You can contact a number of BBQ stores online and they will ship to your hotel. Toby would recommend Hawgeye's I'm sure, the Spice Wine Ironworks and the Kansas City BBQ store are also really helpful from my experience.
If you can't find a BBQ store and can't be bothered with mail order, there's some good stuff to be had in Walmart. KC Masterpiece Honey Sauce is good, KC Masterpiece all purpose seasoning, good too, Sweet Baby Ray's and Bone Suckin' sauces are good stuff. These aren't in the same league as those mentioned earlier but they are still pretty tasty.
As Toby also said, pick up some Lawry's seasoned salt. Also get some bacon salt - it rocks