Phantasy Star 0-Question about Technique Disks

When this game first came out in Japan I got it and totally put a lot of time into it. Now that it's out in America I have it again but I have a problem. I can't seem to find any of the higher level technique disks (Jellen/Deband, Shifta/Zalure?, Melgid/Gantz) You know. The kind of magic that forces can use. I'm just wondering where you can find drops of it because I already checked pso-world.com and it says nothing about the technique disks.P.S. I've already beat the story mode of the game and I'm clearing the extra missions and moving on to hard mode. (Have not beaten the Eternal Tower yet.)

I get my Level 15 Disc from Eternal Tower hardest difficulty.
You know...the one after Hard.

Are you serious? I just beat the Eternal Tower and I still can't find any of the disks. I can only get the basic ones from the female shopkeeper. (You know, the one that sells items?)
And she only sells the basic Resta, Anti, Folie, Barta, and Zonde.
I just need the other spells (Light, Dark, Attack Up/Down, Defense Up/Down)
Without those spells. I fail as a force. D: