I've got a Westfalia BC60 Tow Bar Bike rack, (T5 Caravelle) which also has a Platform or a Box, of which, both can be fitted separately and securely (key) in seconds!
Also, the Box has wheels on the corners at one end, to allow easy carrying.
I believe 60kg is the max weight allowed, so you may want to check up on the weight of your inflatable and sundries?
Hope this helps, other wise it's a 'Fat Max', box from B&Q, with some diy, to complete the fitting and fixing.
Regards.