I second Erik's recommendation of the modern, barrel-shaped screw-in lens hood intended for the Elmar-M 50/2.8. That's what I use on my older 50/2.8 and it also works well on my Summaron 35/3.5 M mount lens.
And Erik, I checked my Summaron 35/3.5 when I got home tonight and sure enough, it does not have the even f-stop spacing of the one you have pictured above. So despite being a goggle-free M-mount Summaron 35/3.5, mine is not the later, rarer one. But between you and me I still like it just fine!
-Randy