All IDs can find the Agito (AUW 1975) Real. The Tollaw drop for Viridia is pretty ridiculous though...I spent endless hours offline doing Gran Squall runs, and never found the thing (my character corrupted
) If you can manage to get your hands on one though, the Orotiagito is a decent weapon...but it only attacks 1 enemy, and with a 3 hit combo. There are 10-star weapons that can do more damage than this.
The only other Katanas that might be fun to use would be Sange and Yahsa. Viridia has a bad Sange drop though (1/351 from Pan Arms), and an even worse Yasha drop.... an insane 1/67217 from Melqueek
If you're online, you have more quests available to you and some of those items might be easier to hunt. If not....heh than good luck.