Internal Pistol grip for 4 inch pipe

I am in the middle of a Protomen cosplay build. For the arm-cannon i am using a 4 inch pvc T-junction pipe. I needed a pistol grip that could house a couple of trigger buttons and I needed it to fit inside the pipe, as my arm is going inside the cannon.

This grip is designed to go inside a 4 inch pipe flush with the 'top' of the pipe. there are 4 bolt holes so you can drill thru the pipe and bolt the grip to the pipe very securely. The holes in the grip are designed for round buttons or swit