I claim the ornamental design for a mountable trail camera visor, as shown and described.
FIG. 1 is a front, top, right side view of a mountable trail camera visor showing my new design;
FIG. 2 is a front view thereof;
FIG. 3 is a rear view thereof;
FIG. 4 is a right side view thereof;
FIG. 5 is a left side view thereof;
FIG. 6 is a top view thereof; and,
FIG. 7 is a bottom view thereof.
The broken lines shown in FIG. 1 depict environmental subject matter and form no part of the claimed design. The broken lines shown in FIGS. 2 and 3 depict portions of the mountable trail camera visor that form no part of the claimed design.