Amazon has Stack-On QAS-1304 Low Profile Quick Access Safe with Electronic Lock.

Slim line personal safe with a removable mounting plate
Solid steel, pry resistant steel door with an extra thick and steel locking plate
Electronic lock can easily be programmed by the use with a "safety key" override
ASIN: B0013LO0F6
Item model number: QAS-1304

Great security for pistols, ammo and valuables at home, on the road or in the office. Solid steel, pry resistant plate steel doors, steel live action locking bolts and concealed hinges provide greater security. Electronic lock can easily be programmed by the user with a "Safety Key" override. Time out period after 3 incorrect combination attempts. Safes have pre-drilled holes for mounting to the floor or a shelf. Fastening hardware in included. Electronic lock can be programmed to beep when the numbers on the key pad are pressed or programmed so the beeps are turned off.
Product Description
Keep 'em guessing! Slimline Stack - On Low Pro Motorized Safe goes anywhere. PRICED LOW! Just 4 1/2" tall... you'll be surprised where you can mount the Low Pro. Predrilled holes on both top and bottom allow installation on the floor, on a shelf, under a counter, under your bed, in a storage locker... even in the trunk of your car. The possibilities are endless. And wherever you mount it, this Safe will stay put thanks to the extra-strong mounting plate that's ONLY accessible from inside the Safe. Be prepared: Solid steel, pry-resistant steel door with an extra thick steel locking plate for added security; User programmable electronic lock with safety key override; Mounting plate and all fastening hardware is included; Measures 9 7/8 x 13 x 4 1/4"h. Weighs 101/2 lbs. A smart investment for the "heater" you depend on. Order Today! Stack-On Low Pro Motorized Safe