I claim the ornamental design for a flashlight mounting device, as shown and as described.
FIG. 1 is a perspective view of the flashlight mounting device.
FIG. 2 is the top view of the flashlight mounting device.
FIG. 3 is a bottom view of the flashlight mounting device.
FIG. 4 is a side view of the flashlight mounting device.
FIG. 5 is a side view of the flashlight mounting device.
FIG. 6 is a front view of the flashlight mounting device.
FIG. 7 is back view of the flashlight mounting device.
FIG. 8 is a perspective view of the flashlight mounting device; and,
FIG. 9 is a perspective view of the flashlight mounting device, wherein a flashlight has been inserted into the device.
The broken lines applied to the article in FIGS. 1, 2, 3, 8 and 9 represent unclaimed subject matter. The broken lines in the drawing figures of the human figure and flashlight represent environment. The broken lines form no part of the claimed design.