You know, this is a very good question. My first solo bard waited forever until he found a scroll of TT. I think there is one in the unseeing eye quest (or maybe that is spell immunity). It is a level 6 spell and I use it mostly for the insta-healing properties -- although the thatco like a fighter helps too!
Check the person that sells scrolls in the Bridge district near that old hut where Neb hangs out. They might have a TT scroll. Ransack the place. You NEED this spell. Well, you don't need it like you need stoneskin or improved haste, but... btw IMPROVED HASTE is the real game-winner here. You MUST get this spell. Cast on self. Now you have 6-8 attacks/round. Impr. Haste is actually more important than TT. I think it's level 6 as well.
Good luck!