i'm willing to help you with a LED setup.
from a cost perspective, the bulb in the first link is going to be the cheapest.
you could also get a custom heatsink from heatsinkusa.com that measures ~5x5" and put some CREE LEDs on that.
im happy to help you select parts, etc. and am willing to do some of the electrical work for you.
what are the dimensions of the tank? what time of hood/lid/canopy does it have?