I don't know if anyone makes a trigger shoe for a mini-14 but I would avoid ANY trigger shoe like the plague.
A trigger shoe that becomes dislodged can lock up the trigger. A trigger shoe increases the likelihood of the trigger catching on something. It's just one more unnecessary part that can cause a problem.
The alleged benefit of a trigger shoe is that it spreads the force applied by your finger over a larger area resulting in a perception of a lighter trigger. A properly adjusted trigger is safe and provides the correct feel and pull weight. There's no reason to add something to that equation that can potentially produce problems.
A solid, one-piece trigger has nothing to work loose or become dislodged. It is protected by the trigger guard that it was designed for and its simplicity is its strength.