I recently inherited a Phil and teds sport which is great and in pretty good nick. DS2 is due any day, and I need to get my hands on a doubles kit, but I've discovered that second hand ones are as rare as hens teeth! I can get a new one from the official P&T website but they are pretty pricey. Does anyone have any idea if any of the doubles kits for the other models would be compatible with the sport pushchair?