vibrating cock rings

I have some credit on amazon. Can anyone recommend any specific models?

Try goodvibes.com. They have had several that I've used in the past. I can't remembe any brands though.

Which ones are best and safest

From my experience they we all safe. What is your concern? I liked the leather ring with snaps. It was easy on and off. The rubber ones can get tangled with hair if you don't groom.

Better still is a vibrating suction tube.