Rush Secret Compartment Boxer Briefs

I have two identical pairs of boxer briefs that must be stitched together so they look, feel, and stretch like a single garment while hiding a slim stash space between the layers. The compartment should... (Budget: $30 - $250 USD, Jobs: Costume Design, Fabric Research & Materials Consultancy, Fashion Consulting, Fashion Design, Garment Construction, Pattern Drafting & Alteration, Pattern Making, Textile Design, Textile Engineering)