To quote from 'Holiday Information for Special Needs Passengers travelling to Orlando', issued by Virgin Holidays. (UK holiday company)
In order to obtain a US parking badge you will need to visit a local Tag Office. You will need to take your own UK Orange Badge/Blue Badge, a doctor's letter to confirm your medical details and some photo identification. The fee for the 90 day temporary badge is approximately $15.00 and should be displayed on the rear view mirror.
The office address is noted below, if you require any directions our local representative in Orlando will be happy to assist you:
Auto Tag Office
11301 South Orange Blossom Trail
Orlando 32837
Tel: (407) 836 4145
Opening Hours:
Monday-Friday 08:30-17.30 (Bank Holidays may differ)
Full details and a location map can be found on this web page:
http://www.hsmv.state.fl.us/offices/orange.html
If you rent a fully adapted wheelchair van, rather than a regular rental car with hand controls fitted, it may well be supplied with its own 'Florida 'disabled' tag, though I suggest you double check with the rental company. ('disabled tag' is the US equivalent of 'blue/orange badge')
I rented a Grand Voyager from 'Rainbow Wheels'
http://www.rainbowwheels.com one year with lowered floor, wheelchair ramp, lowering suspension & hand controls; the full monty!
Pricier than a regular rental, but worth it if you intend to tour Florida and go beyond Disney/International Drive.
Andrew