Victorian glass pear drop shades need metal holder to fit lamp holder. Where do I buy?

The shades originally fitted into a metal holder with a circular hole in the middle for the lamp holder. 3 screws around the rim hold under the lip on the glass shade. The shades do not have a screw top just a small lip. They are heavy cut glass – 3 matching and two odd but similar. The diameter of the glass rim is 82mm.