If you put
cock ring into a google search, you will get more offerings than you can read. Depends on what you want to accomplish with the ring. To retain girth, a neoprene ring will be the most comfortable. Adamandeve.com has plenty of offerings. If you want to retain/increase engorgement for sex, the Osbon ring ($12 with shipping) provides a tight, strong silicone ring which does a great job but because it is tight, it needs to be removed every 15 minutes. I also use a brass ring for sex which requires you to kegel in more blood to get it to retain the engorgement. If you want to save money you can get a rubber "O" ring at a hardware store for under $1.