I bought a universal charger set for my Canon P&S at a photostore in Cozumel earlier this year.
IIRC, if you stand on the pier in "downtown", (1) face the McDonald's, (2) walk straight towards McDonald's, cross street, (3) turn left when you've crossed the street, (4) walk to the very first side street that leads away from the ocean), (5) turn right down that street (I believe that's the same street with the hybaric chamber), it should either be on that street or one of the street parallel to it.
Not sure if that helps, but they did have a bunch of various chargers and stuff, but mine cost $40 or $50 US (i.e, not cheap).