The ornamental design for a side mirrorcover with strap, as shown and described.
FIGS. 1 and 2 are shown with a side mirror cover with strap, on a side mirror, so a shape of the side mirror cover with strap is shown stretched over the side mirror;
FIG. 1 is a front perspective view of the side mirror cover with strap;
FIG. 2 is a rear perspective view of the side mirror cover with strap;
FIGS. 3-7 are shown with the side mirror cover with strap, without the side mirror, so the shape is slightly different as the side mirror cover with strap is not stretched;
FIG. 3 is a front elevation view of the side mirror cover with strap;
FIG. 4 is a rear elevation view of the side mirror cover with strap;
FIG. 5 is a top elevation view of the side mirror cover with strap of FIG. 1, the bottom view being a mirror image of the top view;
FIG. 6 is a right side view of the side mirror cover with strap of FIG. 1; and,
FIG. 7 is a left side view of the side mirror cover with strap according to the implementation of FIG. 1.
The broken lines in FIGS. 1 and 2 show an automobile mirror and form no part of the claimed design.