Adept 1's drop off monsters (chests), as do the uber-rare Mastery versions (much higher than adept).
Adept 3's are made by artisans. For tier one adept 3 spells u need copper or lapis lazuli - very rare drops. For tier 2 (lvl 10 to 19), you need silver - another really rare drop (not sure if there is a lapis equiv). Okay, I'm not sure what the rare metal is for tier 3... sorry, I can't remember.
But to make an Adept 3 for a lvl 22 or so necro pet - u need whatever the copper or silver equivalent is for that tier (tier 3, lvl 20 to 29) - and u need an Alchemist artisan player to make it into a special ink - then u need a Scholar artistan player to make it into a scroll (and he has to get someone to make him a quill and paper). Expect to pay a fortune for this, unless u are lucky enough to mine the rare ingred yourself (or find someone selling it cheap not knowing what it is). GL