I claim the ornamental design for a spa cover lock, as shown and described.
FIG. 1 is an exploded perspective view of a spa cover lock, showing my new design;
FIG. 2 is a perspective view thereof;
FIG. 3 is a top plan view thereof;
FIG. 4 is a bottom plan view thereof;
FIG. 5 is a left-side elevational view thereof, the right-side elevational view being a mirror image thereof;
FIG. 6 is a front elevational view thereof; and,
FIG. 7 is a rear elevational view thereof.
The broken lines showing a spa cover, spa and key in FIG. 1 and rear elements of the design in FIG. 7 depict environmental matter and form no part of the claimed design.