RR Door part help please

I have a 2012 RR 4.4 V8 diesel - what is the little button on the top of the door inside which indicates that the door is open - obviously it goes down when locked - I am missing one, and loosing the will to live trying to find the part number - can anyone help - and even better where to get on from I'm sure it is just a thread on

Welcome to LZ

You could have a plough through the relevant sections on here: http://new.lrcat.com/
But if you've already done that then your best option may be to take the car to a local franchised dealer & ask the parts dept to have a look at the car & tell you what it is.