I have been looking for something similar for my Linhof Techno.
I have been using the Flarebuster for some time, but it's really flimsy and does not keep its position properly, so I can not recommend that.
You should also consider that you will need the option to position the shade for the sun coming from the side rather than from the top.
The Dinkum compact lens shade that sgilbert suggested looks quite promising, is anyone using that? The downside for me is probably the rather short 20cm arm, which might not allow positioning it for light coming from the right (on my Techno, at least).
best,
Gebhard