The ornamental for an electric-assist adult strider, as shown and described.
FIG. 1—Right side orthographic view of patent subject
FIG. 2—Front elevation view of patent subject
FIG. 3—Rear elevation view of patent subject
FIG. 4—Right side elevation view of patent subject
FIG. 5—Left side elevation view of patent subject
FIG. 6—Top plan view of patent subject
FIG. 7—Bottom plan view of patent subject; and,
FIG. 8 is a right side elevation view of the electric-assist adult strider shown in a different broken line environment.
The broken lines shown in the drawings illustrate portions of the electric-assist adult strider in which the design is embodied and forms no part of the claimed design.