Need 8 Shower Door runners?

I had my quadrant shower replaced, which obviously came with a shower door, but the shower door runners that were installed were made of plastic which crumbled and so I need the metal ones which the builder who put in the shower sent me but he sent me only 2 (one top and one bottom) and now refuses to send me anymore :-((
So I am on the hunt to find 4 top metal shower door runners and 4 bottom metal runners as a replacement. I have a picture of the ones I need if that helps. Can anyone suggest where I can get these "Metal" ones please?
Many thanks. Jay