I just got replied by forum support,
The part number of original switch is
KMR641NG ULC LFS
Other switch in the series should work fine as well, depend how much force you need, check out here
https://www.ckswitches.cn/products/switches/product-details/Tactile/KMR6/
but remeber prefix ULC LFS have different function, you can see the explanation here. https://www.ckswitches.cn/media/1907/kmr6.pdf
I guess we must use ULC LFS one.
Probably alot of people already know this, but for some new beginner like me still learning this, hope the info can help someone.