I got the GPO-3 fiberglass sheet from Online Metals dot com. I hoped to substitute it for the more expensive G-10. Looks like it worked. It is smooth like G-10 though in the picture above it looks rough.
This 2 foot by 2 foot sheet was $10. Picked it up myself. Compare to same size G-10 at McMaster Carr at $47 plus some $20 shipping.
The red probably means it is phenolic. Both of these are fire resistant.
The panel looks like it was made with chopper gun, but it will be used for low load applications, so no worry.
They did used to be a friendly neighborhood supplier. They have been bought by Thyssen Krupp and have a new corporate bureaucracy feel now. Good prices though.