What I had done was take several BCT15/996 serial cables (with the female DB9) and cut the small end off and tied each of the 3 (or 4) wires together and then connect them to the corresponding wires from a male DB9 so I could use one Uniden GPS with multiple scanners.
In my original setup I was using a Garmin GPS-III to feed several scanners, an APRS rig and a laptop, again with a custom made cable. On that one I used an old-fashioned barrier strip so I could add and remove items as needed. This was back in the days when a Windows XP laptop running StreetAtlas was high-tech and GPS-SA hadn't yet been shut off.