Most of the stuff on robot shop is pretty small, but it will give you an idea of what is available.
Depending on what your expectations are (carry capacity weight, speed...) you probably will end up finding more powerful gear motors, bigger wheels bearing blocks or whatever you need from other sources. Have fun. I imagine google will help you find examples of other people's projects that are similar to what you have in mind.
I saw an interesting radio control golf club bag last weekend. I don't recall who makes it, but having a closer look at that might get you in the ballpark for what you might want.