I know there is one very close because we forgot our stroller once and ran in and bought one. I want to say that it was in Celebration on International Drive-
the highway with all of the retail right outside of the main gate. I'm sure someone will know a more exact answer, but at least you know that there is one close by! Good luck!
Using the map below, take route 536 (Epcot Center Drive) east out of WDW until you get to Route 535. Turn right on 535 heading south and it will be about a mile on your right. It is close and convenient(within about five to seven miles of WDW)
We used the one on the 535, Polynesian Drive, we got a taxi and it cost around 15 dollars, we also went to the one in kissimee which is a little further away.