I don't know of anything specific, but you might check in Downtown Disney at Team Mickey. It's an athletic gear store that just might have something appropriate for a cyclist. I know they are heavy into the major team sports, but it's worth a shot.
Disney & Orlando Dining/Nightlife, Shopping & Water Parks/Disney Vacation Club
DVC owners at WLV, BCV and SSR
Next up: VWL & POFQ Dec 2009 - just adults!
On Deck: DCL Wonder Dec 2010... but I'm sure we can come up with something before then!