I have a 4 wheel hardside polycarbonate spinner from Delsey, bought over 20 years ago, that has a combination lock plus two key locks and a solid perimeter (no damn zippers). Of course, they don't offer it anymore, since it isn't "TSA compliant".
I've been carrying sidearms within CONUS using it all that time, and never yet had anything stolen.
The airlines have managed to break it a couple times (broke a wheel mount and a handle mount at different times), but so far I've been able to get it professionally repaired with satisfactory results.
I'm glad to know about those currently-available cases as listed by several of the above posters, since my old faithful Delsey can't last forever. I'd thought I was going to have to get a Pelikan (good and strong but really heavy), but maybe not.