[Leica] Lens hood question

[hoppyman at bigpond.net.au (G Hopkinson)]

Folks I have the current Summicron 50 with the collapsible hood fitted.

I am investigating whether there is another option available as a more 
efficient hood . The plan would be to leave the original
retracted and routinely have another screwed into the filter thread. It is 
39mm.

I have noted the various tulip shaped, vented models but would like a 
smaller diameter, with no intrusion into the finder view.
Really, I guess like the little parallel sided rigid hood on the Elmar 2.8 
50 collapsible. I had one of these very compact lenses
but traded it away in support of more exotic Leica glass.

Any suggestions would be appreciated

Cheers

Hoppy