I’ve been playing for a while now and was wondering if there was any other spells not quest specific but spells that can only be found. Example: Bound Dagger and Equilibrium
Including Dawnguard, Hearthfire and Dragonborn the following spells can only be found in the world in fixed* locations (see the links for location information):
* Conjure Seeker can be found anywhere in Apocrypha.
Minor point: Your example of Bound Dagger can only be bought therefor isn't a valid example.