I recently bought a good s/h towbar kit for my P406 hdi estate from a scrap yard, however the four captive nuts that held it to the boot floor rails were past it. I thought these items would be easily obtained from a main stealer. Apparently it turns out that the captive nuts are only available when you buy a complete towbar kit

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Any help / advice would be much appreciated, upon where I could obtain these captive nuts, at a push I could get away with just two.