Oh, I did buy that little Harbor Freight triangle above. So far it works well. I've tied the hook to the stroller bar of my trailer. Balance is off slightly so it tends to shine slightly downward, but still seems to be OK. Three modes. Red solid, white solid, red flash. I've exclusively used the red flash mode..

So far it has survived cold and wet.

The biggest issue seems to be that it is designed upside-down, so the flat part of the triangle goes up, and the point down.