This is really simple to make, and saves getting blood on the bedroom carpet
Step 1: Step 1. Make the circuit
I etched the circuit board myself and soldered the parts to it. I used BC107 transistors for TR1 and TR2, and a 2N3906 pnp transistor for TR3, but pretty much any npn transistors will do for the first pair, and any pnp for the third one. The LEDs I used are 5 volt types, but I’m not sure that they need to be, and I suspect any standard LED (and any colour you like) would work just fine.
Step 2: Step 2. Assemble to the mounting plate
The power consumption can be reduced even more if the circuit is switched on and off by means of a pin switch (like the ones used on a car hood to trigger the alarm) embedded in the hinge edge of the door so that when the door is closed the flasher is turned off and uses no juice at all.