I developed this circuit to install in my rangefinder. I drew it up in Electronics Workbench. It's a basic, alternating flashing (2) LED's.
It works pretty well. I built it in my breadboard, but installed a 250K potentiometer as R2, that way you can adjust the frequency of the LED's(make them flash faster or slower).
I am going to build it into a board that should fit easily into my range finder, and store the 9V battery in my helmet. It's a simple circuit, thought I'd share the wealth. I am more than willing to help with any questions. I will also take any suggestions to any change I need to make.