Bessacarr E665 Spare Wheel

We own a  Bessacarr E665 (first registered Jan 2009) which does not have a spare wheel, only the pump and goo kit. We note from later Bessacarr spec. sheets that later models are fitted with a spare wheel on underslung carrier. As we would like a spare wheel in case of emergencies, does anybody know if a suitable carrier can be obtained to fit the earlier E665 models. I would ask Swift Group, but from previous experience, I expect that we would only be refered to their nearest dealer, who is many miles away. Any help would be appreciated