Tutors for Sorceries?
The following cards in black and green will allow you to search your library for a sorcery, and possibly other cards:


Bringer of the Black Dawn
Cruel Tutor
Demonic Collusion
Demonic Tutor
Diabolic Intent
Diabolic Revelation
Diabolic Tutor
Entomb (tutors to the graveyard)
Grim Tutor
Imperial Seal (tutors to the top of the library)
Increasing Ambition
Infernal Tutor
Insidious Dreams
Liliana Vess (tutors to the top of the library)
Rhystic Tutor
Rune-Scarred Demon
Sidisi, Undead Vizier
Vampiric Tutor (tutors to the top of the library)


I've highlighted the cards with converted mana cost 3 or less.

There are also black cards with Transmute, which allows you to pay {1}{B}{B} and discard that card to search for a card with the same CMC:


Brainspoil
Dimir House Guard
Dimir Machinations
Netherborn Phalanx
Shred Memory


In addition, Demonic Consultation isn't exactly a tutor, but it does let you get a specific card out of your library into your hand, at the cost of exiling every card above it, and with a chance of exiling your whole library without finding it. Spoils of the Vault has a similar effect, except that you're guaranteed to find the card if it's in there, but you lose 1 life for each card exiled.