The Excalibur II is a missable weapon found in
The only thing to keep in mind is that it only appears when your in-game clock reads 12 hours or less. While in the original versions, this was a pretty tight requirement, seeing as it's at the end of the game, in this version there are a few tricks we can utilize. First, you can utilize the x4 speed booster, activated from the pause screen. When this is in effect the game will move much faster, but the in-game clock will still tick like normal. Secondly, both the 9999 damage and no random encounter booster will both help a lot as well. Just be aware that you will be a very low level by the end of the game, so I would recommend spending at least 15 real world minutes gaining some levels at the end of Disc 3, before the point of no return. Level 30-40 should be enough to survive a few attacks from the last few bosses.
All in all, you should be able to get to that point in the game around 4-6 hours, utilizing these strategies.