At AK, Tusker House
At MK, Main St Bakery
At MGM, Starring Rolls Bakery or ABC Commisary
At Epcot, Sunshine Seasons
I also second the idea of just picking something up from Mara and taking it with you while you wait for the bus.
If we're riding the bus in the morning, we grab a muffin/danish, an apple/banana, milk and juice for the kids and then go wait at the bus stop. If we're not ready by the time we board the bus, we just bring it along and eat in the bus. The bus drivers usually just tell us not to make a mess and don't litter, which since it's all hand-held food, is easy enough to do.