BC-1000005 is the Upgrade tender harness.
NOTE!!!
Due to a manufacturing screwup, what they have in stock now has the wrong connector shells, so I'd wait until that's sorted out. I got some of these, and they had the 5V board shells on the connectors, obviously a no-go.
Currently, I suggest the BC-1000002 Universal Tender Harness. It does require you to splice it into the existing harness, but at least it'll work when you're done.