Sorry James, can't help you there.
I can't say I have ever seen that many sleeper cabs on Cargos anyway. I'd say you would need to go around the scrap yards. Another possibility might be to check out Otosan in Turkey or Ashok Leyland in India - they are both still making Cargos - so you might be able to get a brand new one from them but obviously it would cost a lot to have one shipped that distance.
howtomendit.com for free repair help, information and advice.
Try fixfault.com to fix lorries/trucks.