I generally keep a few of these on hand, just get a male and female XLR connector and about 6 inches of wire, and be sure to clearly label it as a polarity reversed cable... someone will use it in the wrong application one day
While you are at it, you can also make a couple these with pin one lifted, in case you ever need to isolate an audio ground... but then I do a bunch of live stuff as well, where this comes in handy pretty much daily.