These options from Fancy Steel https://fancysteel.com/ seem to get good reviews although they are quite a bit more money......a case of "you get what you pay for"?

The small external padlock would solve the broken key concerns (assuming you keep a pair of mini bolt cutters on hand for emergencies)

I see they are going to be attending DomCon. It would be interesting to hear opinions from some Dommes after they had a chance to check them out.