I'm looking for a way to add Charisma to CMB, spells that grapple, pin, trip etc using your main casting stat or the nature mystery, Nature’s Whispers revelation with Agile Maneuvers feat is the closest I've gotten so far and I'm not even sure that one works by raw.
There are several ways, but before anything, remember that any bonus to your attack rolls will also be added to your CMB rolls. So any effect that boosts your attacks will also help your CMB checks.
So, this means that a paladin's smite evil would add your charisma bonus to your CMB rolls. An Order of the Star Cavalier's Calling can add your charisma bonus to attacks rolls as a competence bonus for one check in the next minute. Desna's Fighting Technique would technically apply to spells, as you simply have to be wielding a starknife to gain the benefits. The Bracers of Avenging Knight would allow you to add your charisma bonus to one attack roll once per day.
Followers of Iomedae have some options as well, like the feats Strike True (+4 to a melee attack roll by spending a move action) and Hands of Valor (add charisma to attack rolls for one minute after using lay on hands), or even praying at an Altar of Iomedae to gain a +1 morale bonus to attack rolls. This is merely an example, if you check other gods, several of them will have similar feats, spells or magic items.
It's no wonder that oracle with a dip in paladin is a common build suggestion (Oradin), many of their abilities help oracles.