That's just plain ridiculous. The only place I can imagine seeing it is on "The Office" played for laughs, but Dwight already had a holster and it didn't work out.
Did you notice it's on the "Holsters" tab of that site? They seem to have holsters for every occasion. Well, I guess they missed a few:
Wedding holster -- pockets for ring, copy of wedding vows, secret crib sheet of future in-laws's names, and GPS for finding the church
Movie theater holster -- pockets for tickets, straws and napkins, jujubes (with dispenser), and hot butter-flavored oil
Exotic dancer holster -- pockets for dollar bills, keys to locker, dance schedule, and other bare essentials for when you just don't have any other options