A 1.6-pound polycarbonate travel lock box with a rubber over-mold, a key lock, and a 1,500-pound-rated cable, sized for up to a full-size 1911.

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SnapSafe TrekLite Lock Box, X-Large, Black/Gray - 75212
The TrekLite Lock Box XL trades the steel XL's six pounds for impact-resistant polycarbonate at 1.6 pounds, with the same 7 by 10 by 2-inch exterior. A non-slip rubber over-mold protects the shell, a foam lining keeps the gun from being marred, and SnapSafe says it fits handguns up to a full-size 1911. It ships with a 1,500-pound-rated security cable whose connector does not eat into interior space, and SnapSafe lists it as meeting TSA requirements, which makes it the lighter pick for a suitcase or a backpack. Two cautions: the shell is polycarbonate rather than steel, and SnapSafe states that TrekLite boxes are not California DOJ approved, so California buyers should take the steel XL instead.
Add the SnapSafe TrekLite Lock Box XL, Keyed (75212) to your build and see how it enhances your platform.