I've got a mahoosive one for sale. 6'6" long, 2'3" wide 14" deep. It's German and really well made - cost me £150 and only been used twice.
It used to fit nicely on the top of me LWB Shogun and would be ideal for a Disco.
It's totally weatherproof and comes with 2 keys (strong locking system) and all the fittings.
Make me an offer.