bike rack/carrier

i was given a bike rack that was taken from a disco 2, it's the type that fixes on the tow bar, it came from a friend of my brother who lives miles away from me, anyway my bro fetched it when he was visiting, it doesn't look like its been used, but the plank sold the disco with the vital bit still on the car ( the bit that's clamped between the tow ball and the bracket ) does anyone know if this bit is available seperately? it is a genuine land rover bike rack, maybe the person who got the disco is trying to get the rest of the bike rack