Google Fi
If you can load up your phone with an e-sim, three hk has some pretty good offers:
https://www.three.com.hk/prepaid/DIY/en/offer/travel
365 days to use 13GB globally for $268.
CAUTION: Most iphones sold in HK do not work with an e-sim (I learned the hard way).
They send you a QR code and you can scan it to add to your phone. However, if your phone does not allow for e-sim, the QR code won't do anything.
My wife is using the 35GB for $268 in US with a borrowed iphone that was purchased in the US. Traffic gets routed from the US back to the HK network.