Carrying second spare wheel on a VW Transporter is a dilemma for me. Inside the camper is not an option – there is not enough room and roof racks are not a practical option for two reasons:

I could not lift a wheel above my head and adding roof racks to my lifting roof is not a practical option as it is a fibreglass construction and I do not have the clearance under my house for racks.

The only options that seem to be possible are mounting a spare on the tow bar/ball or fitting it to the back tail gate.

Image t5-t6 Upgrades UK.

The Hess Automobile product is possibly a better option as it allows for more rear vision if you only mount the wheel, but and also lets you store a second item on the back door.

Hess Rail Racks

Another tailgate mounted option is by 50degnord

Another possibility that is tow hitch mounted is the Mirack – made in Australia tilting or swing away