I don’t think anyone has designed an expansion board with only GPS. But there’s a discussion thread here that indicates there are some boards with LoRa and GPS:
As far as I know, Clockwork doesn’t sell the 4G expansion board separately anyway, although you could contact alex@clockworkpi.com and ask.
I’m not familiar with USB GPS options, but that may be a possibility too. With something like this expansion card, and maybe an adaptor, you may be able to find a small enough USB GPS unit and put it inside the uConsole case. Plus you’d gain three external USB ports. While I haven’t used it with GPS, I own one of these expansion boards and it works well.