Some of the best locks are very very hard to buy as well and still protected with weird export controls held over from the encryption export days.

I frequently use FF-L-2740 spec locks, which is the spec locks need to hit for use in classified government work, military contractors etc. They are very good locks I can't begin to defeat in any practical amount of time and don't know anyone who can. Particularly since they have timed brute force lockouts.

Problem is not a single vendor is allowed to sell locks of that spec to civilians by contract so you have to jump through lots of hoops to get them.