A few places you could look include http://www.delphiglass.com, http://www.slumpys.com/SlumpysStore and http://www.colourdeverre.com. I’m not sure what country you are in but the service from the states isn’t too bad if you live down under.
Alternately you could consider just fusing 2 layers of glass together and then tidying up the edges by coldworking them, depending on what depth of glass you are after.
Good luck with them
Perth, Western Australia