stealth bag
n. A bag or purse designed to disguise its cost, wearer, or contents.
Examples
2006
Designer bags now regularly cost a month's rent. They've spawned their own jargon, from "It bag" and "arm candy" (both already passe) to the current "stealth bag"—an expensive purse made by a lesser-known artisan.
—Andrea Lee, “Bag lady,” The New Yorker, September 25, 2006
1998
Stealth bags
When Rex Moser of Washington arrives at his tourist destination, he goes to a local mass merchandiser and makes any necessary purchases. "The real prize is the store's plastic shopping bag with the name and logo prominently displayed," he told The Washington Post. He uses the bag to carry all his day-trip necessities and often passes for a local resident, fooling thieves.
—Michael Kesterton, “Social Studies,” The Globe and Mail, June 08, 1998
1997 (earliest)
Stealth Bags
To protect your computer and accessories while traveling, it's common to use a bag. However, what the bag looks like can determine whether you will be recognized as a target. Black computer-case bags are the major tip-off that you have a notebook. We looked at computer backpacks from three vendors who specialize in computer cases and products: Kensington MicroWare, Port, and Targus. Our aim was to determine how well these bags disguised their cargo.
—Bruce Brown, “Stop, Thief!,” Computer Shopper, May 01, 1997