Your 550 must be getting power from somewhere but none of us have seen your bike.
The easy guess is:
(i) It gets its power direct from the battery, or
(ii) If your bike is a BMW, maybe it gets its power from the dedicated GPS feed, that is usually hidden away somewhere up the front of the bike.... or somewhere else, or
(iii) It's getting its power from somewhere else entirely, where maybe the BMW fellow has tapped into a convenient power supply. For instance, the rear light, perhaps?
As you haven't told us what your bike is or much else, that is what you are maybe stuck with.
Me? For now I'd assume option (i) or maybe (ii) not necessarily in that order. Can YOU, starting from the cradle end work your way back down the lead to find it plugged into a socket? If yes. Unplug it; you probably can't break anything. What happens then? Is it all unplugged? Great, job done. No? Keep on following the lead and / or go and look at the battery end. Does it look like it's wired to the battery? Great! Unhitch it from the battery. Job done. No? Go to option (iii).
Failing any of that.... Go to BMW and ask them to remove it for you.
Vis-a-vis the bike you are buying and will it take a 550 mount instead? Logically, yes. It's possible to fit just about any GPS cradle to any motorcycle.