I realise there is a fine line between providing information and creating a potential GAS attack, but Howarths in London have a second hand mouthpiece sale at the moment. They have loads on their site, some at very good prices depending upon what the sellers want for them (commission sales via Howarth I believe). I rang yesterday about a metal Yani that was 2 years old, no problems, and sold for £60. New price is around £215. Not everything is as good but worth a look if you're on the hunt. There are vintage pieces too.