Hey I work as a Lab tech at a pretty big eyeglass company.
I'd suggest getting a set of plaino (no perscription) gold mirrored sunglass lenses.
heck, I bet I could cut them to the size you wanted (or template)
just from eyeballing it, I'd say that the best match for a base curve would be like a 6 or 8 base lense.
I immagine polycarbonate lenses would be easier to obtain in your area.