Hi- we've just started shipping a revision to the GPS board that uses a U.FL connector and very small external passive antenna. I apologize that our product listing does not show this- we're in the process of launching a new website/web store. This is not a great situation- I'll push for an updated listing ASAP.
Regardless, the external antenna greatly increased performance as you would expect, and it seems to work fine with other small passive GPS antennas.