gglabs.us offers a DB9 RS-232 breakout and monitoring kit. It consists of a pair of DB9 connectors separated by a PC board. While sturdy after properly constructed, I worry that the bottom of the board may short out if it comes in-contact with something conductive on the workbench, and an accidental 'bump' while connected to a device may damage the connectors.
This 'sled' case eliminates the risk of short circuit on the bottom of the board, and adds additional rigidity to the connectors.
The board fits into the case and stays put with a friction fit. The DB-9 connectors have just enough burr to 'grab' the enclosure, keeping it in-place. If your case is too loose, some double-sided tape or glue should hold it in-place.