Somebody was making the black/silver plastic insert, which is the difficult part to obtain. He'd given up trying to buy one and had made a small mold to cast a couple of them.
I think it was on the Elan forum - Lotuselan.net, either that or the Yahoo group. I'll look later and if I find it I'll post up. Once you have the "Lotus" bit then you can use the rest from a Triumph horn button, or anyone else's come to that.
Brian