Here is the set-up I promised to photo for you:
Eye-Bolt was placed "eye" inside a piece of hardsided luggage. Plastic coated cable was attached through the eye.
This is the outside of the bag. I epoxied the nut to the threaded portion of the eye-bolt. The white piece of soft plastic covers the remaining threaded portion nicely. All this stuff came from a local ACE Hardware store. Nothing exotic here. Do note the two washers I used, one on either side of the shaft of the eye-bolt (one washer inside the hard sided luggage, the other placed on the outside).
This is the other end of the plastic coated cable. As you can see I fasten the cable using the same hasp lock I use to secure my Pelican hard sided case. Note the weapon card. Put there the last time I flew via JetBlue. Yeah, I know the regs. Go figure.
Will this absolutely prevent me from losing a handgun when I fly? Nope. But it will make it a heck of a lot more difficult for some mutt to simply just take my handgun case from my luggage.