I don't know about that harry, the page contains lugs going down to 10mm.There is absolutely nothing on that page, which I would consider as slightly useful to your problem.
All you need, is either a hole in each metallic part, a nut and bolt, plug suitable small cable lug, OR - instead of the nut and bolt, a self-tapper. The meatal bracket, and metal lamp-holder, both need to linked together by wire, and the wire terminating in a connector, into which your earth wire from the wall cable, also goes.
But Pete had linked to a combined lug and terminal
