You can 100% do it yourself, though I think the fact that it has GPS makes it a bit of a weird area because it starts to become a radio even if it's not an intentional transmitter (I've had people who work at EMC test labs tell me they don't understand WTF the standards are actually supposed to mean for GNSS kit). But for a regular electronic gadget you don't need a lab with the right certificates or anything, it's just a declaration on your own liability that you think it meets the required standards. If you're happy to do this yourself and that gives you enough confidence to sign it off, you can. (And in practice the regulators don't really come knocking for small stuff like this unless it's somehow doing something catastrophically bad)