I have not with the Universal Hotels but did rent one on our last trip to Disney for my Grandmother. Booked through Randys Mobility, they delivered to the hotel on the date and time we asked and they picked it back up on the date and time. I am sure they could deliver to Universal. They had several sizes and with or without canopy was an option.
Check the disABILITIES board for other options and reviews and even tips on steering them!