Trap it!

Ibanez has this Trapper strap (but I don't see it in stores here) with a locking strap-end contraption. It's a ready feature so one would not invest further in locking attachments to be used with one's strap.

As you can see here, the strap click-locks the strap button in place, you just have to push it off to unlock. I wish to have a closer look at this strap... if only it's available here.