FF X: Making your own super weapons.

Let's just say that I have little chance of aquiring and completely unlocking most of the "Legendary Weapons", and since I happen to have many of the items that I need to put my list of Über abilities on weapons and armor myself, it seems that I just need weapons and armor with 4 open slots. Only problem is that it seems no one is selling them...the best I've been able to come up with is that the Black Element has a 50% chance of dropping equipment, and the equipment will have 2-4 slots, 0-2 of which will be filled. Is there an easier way?