This specific one is for a cable lock, I have one of these myself (as a secondary lock for the front wheel while it's locked in the storage area).

https://www.amazon.com/Coiling-Resettable-Combination-Complimentary-Mounting/dp/B0151RQAX2

There is a u-lock that has a very similar mount, but the button is a little different.

https://www.amazon.com/SIGTUNA-Bike-locks-Shackle-Bicycle/dp/B016GZWRY4