Does anyone have a good source for thin glass for making ground glass?

For some cameras, the ground glass needs to be pretty thin - about 1.25mm, or .050". Some years ago I bought replacement picture frame glass at Michael's, but they no longer carry pre-cut replacement glass. Hobby Lobby and others all seem to carry 2mm glass - which is fine for most purposes, but won't fit well into the Ciro-flex F TLR I'm working on.