My golf Tdi has got a bilstei suspension kit fitted to it and one of the rear springs broke last week

. I think its a streetline kit thats fitted to the car (black dampers and red springs) and was wondering if anyone knows where i can get a replacment spring from? Ive tried looking on the internet but can only find whole kits.
Or does anyone know if any other make of lowering springs would fit the bilstein shocks?