Angled Foregrip With Compartment

This is an airsoft fore-grip that attaches to picatinny rail, it has a compartment in the back for an extra power bank and other things that are small. you could even take the model and put a hole in the back-cap for a cord that runs through into a phone or scope camera etc.
It takes 8-32 1 1/2 inch screws and nuts that will hold in place tightly (careful not to crack it).

The fore-grip also has a longer front drop-down so you can also put your hand there for a more vertical grip.