Hopefully some one can help?

I need to know what diameter the DW Link post mount nuts are (sit under the post mounts for the rear brake and contain the thread for the standard mounting bolts)?

I’m building up my friend warranty replacement Lapierre 514 frame and due to some very poor customer service the similar mounting nuts have not been included. I was hoping the Turner ones would fit as trying to get Lapierre to provide them appears to be similar to getting blood from a stone.

The holes on the Lappierre are 9mm.

Thanks