| The only way to comply with the TSA regulations is to check a bass unlocked. Should they encounter a locked case of any type, a bass, a suitcase or whatever they have the right to break open the lock to inspect it. Often though, the TSA officers inspection station are in plain sight, near the check-in counters. The last time I flew I presented my case unlocked and stayed nearby while it was inspected. After they had their look inside I very politely asked the inspector if he would be willing to lock the case up for me afterwards, since I'm not allowed to touch or handle it after the TSA clearance. I handed him my hex key and offered instruction on how to properly lock it. The TSA guy futzed around with it for a half a minute, but couldn't manage to work the lock, as he was wearing rubber gloves. He finally just gave up and invited me into the inspection area so I could lock it up myself, under his watchful eye of course. This was "against the rules" but he must of figured that I was OK, just a bass player concerned about his instrument. I wouldn't expect to have this sort of luck the next time though, so I'd just rather send it thru unlocked, rather than risk damage to the case or worse, the bass should they opt to break the locks to have a peek inside. Since 9/11 I have never been simply waved thru an inspection, even after the case has been X-rayed they always look inside.
About a replacement key for your Gage case, my Gage case for the Czech-Ease uses a hex key, goes in the holes in the case on either side. I couldn't give you an exact size to buy offhand. I'd just find a decent hardware store and buy a few in different sizes that look like they might fit. You most likely would bring one home that fits out of half a dozen or so that look like they might. Couldn't cost very much, a few bucks at the most. | 
