There is a VERY small shop before the ticket gates, but it's really aimed at people leaving the park who might have forgotten to pick up a gift from the main shops inside.
It's tiny and so I wouldn't rely on it having very much in the way of interesting stock. Plus I guess you'd have to walk across the car park from your hotel to get to it as I doubt you'd want to pay $30 to park a car if you weren't intending on actually going in to the park.
The shop at MCO would be a much better bet.