Then try Schott in Sydney - I've rung them & confirmed that they will supply 25.4mm thick Borosilicate (Borofloat 33) water jet cut to whatever diameter you want, within reason. I'm not sure what the sheet size is that they cut from, but unless you're grinding a 2 meter mirror I don't think you'll have problems hehe....
So there shouldn't be any need to panic about Pyrex no longer being manufactured since the Boro will do the trick.
They currently have a sheet in stock (made in Jena, Germany I believe) that they recently imported for someone in NZ who required a blank. But obviously they don't get a lot of demand, so if we can generate some then they will be more inclined to continue stocking it eh?
You can contact them at:
lesley.aitkin@schott.com or check out the web:
http://www.schott.com/hometech/engli...oat/index.html
Cheerz.....