Here’s where I bought mine from. http://www.esslinger.com/watchcrystalsflatmineralglass.aspx
All you need is a micrometer to measure the diameter and thickness of the glass once you get it out.Ater taking the back off and removing the “guts”, the crystal just pops out through the back. There is generally a plastic ring around it,just save it for the reinstall.The biggest downside is the shipping and waiting, I did call around and it is a bit pricey to have it done by a jeweler.
