[useryman]

From working on hardware with GPS-functionality tacked on before, I can suggest a simpler solution;

1: Find the GPS module, and look up its data sheet.

2: Spoof the data coming out of its IO ports. Cheap GNSS modules that spit out NMEA messages on a serial line are everywhere. (I guess because they're super cheap, and easy to integrate)

[jandrese]

If it is a separate chip this is a good solution, but these days you're more likely to find it integrated into something else.