I've been on the hunt for "OEM" style N64 sticks as well, but so far have not found anything that didn't scream "junk". I know there are a few projects out there, like Steel Sticks 64 but there hasn't been much talk of anything actually produced that'd be superior to what's already out there. This place sells the parts that wear out the most, but I'm not sure about their stock. "Gam3Gear Replacement 3D Joystick Thumbstick Repair Parts for Nintendo N64" read to be highly recommended on Reddit but I can't find anyone that has stock in it, not even on eBay.

I got a Gamecube style stick from The GOAT Store and it feels pretty good. I could manuever and do acrobatics with Mario in SMB 64 and could hold my own in F-Zero X but I haven't really put the stick through any rigorous testing yet. I couldn't detect a "dead zone" as a slight nudge and Mario began to tip toe but it doesn't take much to go to a walk and then a run.