hmmm, what have you tried? Are in the waist band not an option? You can be 350 and not a huge fattie, or you can be a 350 pounds of just fat. Sounds rude, but theres a difference. Anyways Get a good belt, and a good holster.
I would have advised against such a small gun for a large guy! Its not like you are having a hard time concealing the gun, so a 23 or 22 may have "fit" better on you.
Uncle mikes makes some good shoulder harnesses, but get the belt attachments so its not bouncing all over the place.