I would recommend thumbstick covers. Something to cover up the actual rubber, and would be easily replaceable.

https://www.amazon.com/eXtremeRate-PlayVital-Joystick-Silicone-Controller/dp/B08KS5GBN8/

That kind of reaction is usually due to your finger oils/sweat being excessively acidic. If thats not something you can resolve, then its going to continue happening to new thumbsticks.

However there is full replacement thumbsticks too. But swapping those out requires tearing apart the whole controller.

https://www.amazon.com/Analog-Joystick-Nintendo-Controller-Replacement/dp/B0B1Y7JL75/

https://www.ifixit.com/Guide/Nintendo+Switch+Pro+Controller+Joystick+Caps+Replacement/127789