These smoked perspex visors came with my Roadster and I think may have been Simmonds. They were available in grey, blue or green tint, but are not available now as far as I know. Neil has a very valid point about possible injury, and I would also point out that if you don't have visors, but have the tapped stubs on the screen frame, you should consider fitting some rubber covers, because they could be nasty if you hit one with your head!
I reversed the brackets on mine so that there are no sharp edges, and covered the countersink screw heads with screw head caps. They are also fixed in this position, but will bend when 'forced'. They fit under the easy up without moving, but also note that the edges are an interference fit with the mirror, and with the header rail catches, so they 'only just fit'.
On Bumble, I found a seller on e-bay selling the same visors for Minis. The Mini brackets are a few mm closer together, but I asked him to make me a special pair up, which he did. The perspex is the same size as the Mini, but the brackets are moved out to the edges. The only difference is that with the standard hood, they have to be lowered very slightly with the hood up.
They are better at wind deflection than visoring, and in rain, the droplets get blown up the incline and drop on your lap. But they look good and I love them.
This is TM you know, not one of those other forums. 
