Following up here. My search for something that fits the regs located
here and is ready made turned up zilch. CNC cutting was fun to look at but seems to have a minimum charge and isn't geared toward economy. Also, as I might have stated earlier, I live in a small apartment and don't have access to serious woodworking tools, so building something from scratch is a bit difficult.
I wound up going to Home Depot and buying two $12 sheets of 3/4" MDF, then having the guys there cut it into panels for me. Some brass screws, hinges and a clasp later and I'm good to go. For the curious, here was my materials list:
4 x 3/4" x 20" x 12" MDF (top, bottom, front, back)
2 x 3/4" x 12" x 10.5" MDF (left and right) (get 4 of these if you want internal divisions)
2 x brass hinge kits (I used three hinges)
1 x brass locking hasp
4 x #8 5/4" brass screws
I also got some weather stripping for the lid (not sure if I'll use that) and self-adhesive felt feet so I don't scratch up the laminate flooring in my apartment. I actually wound up with 2 extra 10.5" x 12" boards, so I just jammed them into the box to create some dividers.
The Home Depot guys will cut your MDF as accurately as they can with their big wall saw, but it's always going to be a bit rough. When I gave the guy measurements in millimeters he just laughed and said he couldn't get that accurate. But the cuts he made were plenty accurate for the rough box I wound up throwing together on my kitchen floor with nothing but a cordless screwdriver.
In retrospect, I should have used something other than MDF, since it doesn't seem to hold wood screws very well and is heavy as hell. I also started out with larger screws (you can see some cracking in the pics). But I think I wound up with something that should meet the letter of the regulations for a total cost of about $60 and some time. I just have to spray paint it, put the word 'explosives' on the front, and add a brass padlock, and I should be in complete compliance with the regs.
I realized many people in this thread don't really care about the storage regulations -- this is for the people who do. If anyone else wants more info, feel free to PM me.