Here's a little cheat to get those powerful weapons faster. Here's what you have to do. First activate the configuration mode and select yes when ask if you want to control enemies. Next enter a battle with enemies that have those rare weapons. When you take control of the enemy, make him discard his weapon(if he has one). After that you can either cast Egress or finish the battle. Finally go to any town, enter a shop and go to the DEALS option. You should be able to find the weapons you discarded from enemies in earlier battles. You can also "steal" any ring and rare item that enemies may be carrying.