I keep a revolver(S&W M10) in my breif case. I have a Breif case that was made for a gun by Dillon and is only a zipper away. I keep laptop equipment in it and everyone at work is used to seeing it next to my filing cabnet under my desk.
I would look for a larger gun to cary.
The Ruger LCP, Seacamp, Walther PPK/s, Beretta Tom cat, Colt Mustang, Sig 230, or the new Sig that is tiny. Saw one this week at Cabela's in Reno and it was 2/3 the size or smaller than MY P230 or Walther PP Similar to the Colt Mustang. Or a S&W 5 shot J frame. All can be worn in an ankle holster. The others can be worn in a pager or pocket holster. There are also wallet holsters for guns like the Beretta and the Seacamp. (check local laws on the wallet holster. They are illegal in places like Communist California) Other options are to keep the gun in a leather binder. Again Dillion makes some that look like day planners or bible case and can be kept in a breif case or even on your desk with out calling attention to it. You may want to get two and use one as a day planner or bible cover.
While the NAA or the Derrenger are better than the stapler I would rather have something larger, in size, capicity, and caliber that can be reloaded by either a magizine or a speed loader.