Dana:
I saw some LED Xmas light strings this past season. They came in white and in blue. I thought of getting one for spare bulbs, but then I looked at my wallet and decided the money was better spent on necessary purchases. If I see any around I will buy a string of 100, though.
I have two white lights on my 10, with an old calculator power supply of 4V DC. They shine brightly and are more than enough for the tank. My 2 lights came in an expensive (around $25.00) unit, though.
Rafael