I am not quiet sure you will easily find faceted Quartz the size you
need without having someone cut them for you. You might find white
Spinel and more likely find White Sapphire.
There is a source you can try called House Of Onyx here in the U.S.
Their prices are a little high but you might find what you are
looking for. I don't have their contact but they do have
a website. I believe it is www.houseofonyx.com
Before you order stones let me bring something to your attention. If
this is an 18th cent. Watch you should be using either rose cut or
table cut stones to make it look authentic. You will need someone to
cut those for you so you should be looking for a lapidary.
Custom Jewelry - Handmade Jewelry - Antique Jewelry