The people who said you should be able to find this drain are absolutely right.  Your clock should not drain enough to kill a battery in a few days, but it might add to the problem.  Get a very sensitive inductive ammeter, and keep disconnecting things until the drain goes away.

You can rewire your whole car for about $1,000, and that will fix any "old wire" problems, but that won't help if it is the voltage regulator, horn relay, headlight switch, etc.

Good Luck