Most likely it us a cock sheath bulge...here’s an example... they are made of very stretchy material...
http://2.bp.blogspot.com/_CvbzTiansAo/TSH-U_K3AiI/AAAAAAAAAgg/EOSa8DC8Ix4/s1600/CockSheath1.jpg
Also looks as though he has some assorted probably neoprene cock rings on hand as well!