The Cooke is like a $2,000 lens. Out of my price range for now! I understand why you enjoy yours so much!I have diddled around a bit with LTM lenses and rambled about boards and listened to the propeller heads who know lenses. One recommended is the Jupiter 8, KMZ the best bet and early if possible, like early 50's. I have a '57 which is very kind. I have two or three others including a '51. I have to get the '51 shimmed for the M9. But to get a virtual pre-war Sonnar for less than US$100 is a good deal. I was advised on the Canon 50mm f/1.8 manual focus and it is good, very good. But for 50's you know I am opting for the Cooke Amotal 2" f/2.0 which is so sharp and also has a glow to it. I hunted for a few months before I finally found a good copy and from an honest seller. So those are my three fave 50's. I have a Canon 35mm f/2.0 which is OK but not a soul grabber. The CV 35mm N II works well on the M9 and I tend to that. Shorter focal length for me is the Canon 28mm f/2.8. It is fine on FF and an effective 35mm on APSC like the Pixii. It is great with color or B&W and quite sharp. And for longer I have the 85mm and 135 Jupiters, both good copies, which, again, are Sonnar copies.
So I have gotten by pretty cheaply in lenses. I have good lenses for me. In FF I go 50mm mostly and that is #1 Cooke and #2 Jupiter. These are pleasing enough that I have pretty much stopped lens GAS. I think.