i would try the others user about the Toilate, if that dont work, tell him to wear a pull-up, if He wont participate in the activity, why waste time on laundry? if he refuses it, just put a diaper on him, Tape it if he takes it off...it sounds like you tryed, tell him to come to you when hes ready to participate.
Do you mean a 'potty', or the toilet? My son totally refused the potty and insisted on using the toilet - and refused to sit at all. If it's a potty that you're trying to train him on, perhaps get him a stool and allow him to try standing like a 'big boy, just like his dad and older brothers' for the toilet.
In general it sounds like you're being patient, which is the right thing to do. I'd usually suggest simply continuing what you're doing. But, I have the sense, even from your brief description, that he's harboring some particular fear/worry that is worth investigating. Ask him: "The other day, I noticed you were holding onto your penis and not wanting to use the potty. Is something the matter? What do you suppose would happen?" See what he thinks.