Have you tried somewhere like Euro Car Parts or similar?
Halfords do cheap stick on door guards for about £20
Short (Ripspeed) - http://www.halfords.com/webapp/wcs/..._productId_205321_langId_-1_categoryId_246902
Long (Ripspeed) - http://www.halfords.com/webapp/wcs/..._productId_198759_langId_-1_categoryId_246902
Stainless steel (Ripspeed) - http://www.halfords.com/webapp/wcs/..._productId_373751_langId_-1_categoryId_246902
Stainless steel (Richbrook) - http://www.halfords.com/webapp/wcs/..._productId_796981_langId_-1_categoryId_246902