Thanks graybeard. I found this gun safe (for 1 - 2 handguns). It's pretty substantial for a semi-portable secure case. It has both push button combination and key lock override. I just need to mount a bolt on plate to put a cable through for locking to a steel seat frame when I travel with it.

http://www.exploreproducts.com/adgsports-securevault-topload-handgunsafe.htm