You can get those scrolls at Ribald's special wares but only after you come back from the Underdark. They're a bit expensive though (about 10,000+ gp I believe). BTW, this time around I went straight from Irenicus's dungeon to Nalia's keep, the to Aran Linvale, then to Bhodi's, then to the Asylum. I'm finally out of the Underdark, but Imoen and Nalia are within 7,000 exp of each other. I do all my side quests in chapter 6 after talkin with Elhan.

Hehehe.. That's when I did my quests this time around.. After I killed Bohdi, I kinda just took it easy, wandering the streets of Athkatla, making plans to vacation in Calimshan, dinner with Renal Bloodscalp, sleeping for weeks straight to trigger stronghold quests, feeling occasional pangs of guilt for abandoning my elven kin, getting drunk, and having a grand old time.