Where to find 1m Rear Quarter Panels

[lavanlint]

Does anyone know where the rear bmw 1m e82 quarter panels can be sourced in the UK?

I am currently in the process of converting my 135i to a 1m body but I cannot find the rear quarters as they have all been discontinued.

I am trying to avoid the route of using fibreglass panels as I want the car to be as durable as possible and the car is used somewhat frequently.

Part numbers are:
41008052627 BMW Left Rear Side Panel
41008052628 BMW Right Rear Side Panel

If anyone can help that would be greatly appreciated!