Are there any items to boost exp gain?

The Unit Medius (3 to 6 Stars FFBE Unit) Has a Growth Egg as Trust Master reward. Its Description says:

Whoever is fortunate enough to acquire the growth egg will earn battle experience at a much faster rate, as well as quickly gain knowledge of magical spells and abilities.

I haven't mastered it myself, so I might have just traded one grinding for another. Other than that I have seen nothing so far.

Edit
The trust master reward for Nine is Action, which boosts EXP by 50%.

In the Year 1 Anniversary event, there is a reward item 'Anniversary Ring' which has Exp x1.3 bonus.