(G) Doblo van with high roof (not elevating)

I am thinking about getting a Doblo van (not latest shape) to use as an everday vehicle but also as an occasional camper/overnight sleeper for away weekends at dog agility shows. As security is more important than style or interior light but additional height would be a bonus, I am looking for a van with the high roof option - the full metal one, not the glazed version fitted to the people carrier/taxi option.
It seems hard to find a van with this option - does anyone know if there were many made or if the roof extension can be retrofitted?

Doblo high roofs are a factory option I doubt theres a retro fit available if there was it would probably cost more than the car was worth. However there are plenty available most are ex mobility wheelchair conversions possibly cheaper and with lower miles than a conventional doblo.
http://www.motorspeedportsmouth.co.u...ateststock.htm

I notice they have a 2010 (60), 1.4 for sale, described as a high roof but the pic shows a standard roof