LED Lamp
Perfect for portable use, powered with a 9 volt battery.
I built two different types of lamps. The first was the goose neck lamp using the superflex and plastic clamp. The second one is simply a plastic Coke bottle cap with two holes and a 9v battery clip.
The complete lamp. Built using an 18 inch length of 1/4 inch superflex heliax, two white ultra bright LEDs (Electronic Goldmine), some heat shrink tubing, a 100 ohm 1/4 watt resistor, two tie wraps, one 9 volt battery and the end from an old one for a connector, a drop of silicone sealant on the base of the LEDs and a plastic spring clamp.
The two LEDs produce more than enough light for operating and logging.
You can clamp it to almost anything...
This is the simple bottle cap lamp. The cap has two holes drilled in the end for LEDs. The LEDs, the resistor, the wires and the battery clip are all potted in J-B Weld.
And the schematic is simple.

Using 100 ohms for R1 the LED light will draw 20 ma from a fresh 9 volt battery. After over 24 hours of continuous operation, the voltage is down to between 7.4 and 7.5 volts which is right in line with the "Typical Constant Current Discharge Characteristics At 21 degrees C (70 degrees F)" graph that Duracell provides here:

I decided to change the resistor to 330 ohms after running the light on 100 ohms for so long.

Duracell appears to do a good job of providing battery data for all their products:

High brightness LEDs are available from many sources. I buy mine from the Electronic Goldmine, http://www.goldmine-elec.com/. Their prices are good and delivery is quick. The last ones I bought were $0.99 each.