I know most people don't like the idea of using LEDs without a resistor, but since you have a 12 volt power supply, try 4 LEDs in series, no resistor and see if that gives you enough light for your project. I speak from experience, I have a light on my bench that is 4 in series, on a fan cooled heat sink and they have lasted for months so far, I also use the same set up on my off road vehicle, putting 6 string of 4 tied directly to battery power via a switch. Haven't burned an LED yet and I have run them for hours at a time.