Just get a float valve ATO. Can't beat the old reliable systems. All plastic and rubber and only one moving part. Bullet proof. And cheap. You can tie the 1/4" hose into a cheap low flow aquaclear powerheads pump using a 3/4" to 1/4" reducer.
https://www.amazon.com/AquaClear-Pow.../dp/B00025656Q
This style in particular. You can leave the air line input on the pump output open. That way when the float valve is in closed position the pump can still move some water and not seize up.