Excluding the use of duct tape, I can't think of a decent-looking way to do this. You're probably better off going out and buying the whole LED Fan, anyway, instead of buying individual LEDs and trying to daisy-chain them up and attach them to a power source... it would be a lot safer that way, too...
A good, cheap LED fan won't cost you that much from NewEgg - maybe $5-6 or so. $10 if you want higher airflow.