Idea of Flash Off Icon
An hourglass shape that has the bottom left corner and upper right corner extended slightly further than the rest. The hourglass is leaning thirty five degrees to the left. there is a line running from the upper left through the center of the hourglass to the lower right. The straight line extends past the top and bottom of the hourglass.
This page shows the different variations of the Flash Off from an Icons8 icon pack. Feel free to resize and recolor the icon, and then download the icon in PNG format for free.