The ornamental design for a shockextender, as shown and described.
FIG. 1 is front perspective view of a shock extender.
FIG. 2 is rear perspective view thereof.
FIG. 3 is a front view thereof.
FIG. 4 is a rear view thereof.
FIG. 5 is a left view thereof.
FIG. 6 is a right view thereof.
FIG. 7 is a top plan view thereof.
FIG. 8 is a bottom plan view thereof; and,
FIG. 9 is an exploded front perspective view thereof.
The broken lines showing the nut and bolt and threaded portions are for the purpose of illustrating unclaimed subject matter and form no part of the claimed design.