Hy wildatheart76, welcome, the o.e.m. part number for the cap is 5455826 apparently it had the words "use GMC Brake Fluid" in raised letters. I have no picture and I can't remember if it had a hex shape or a square shape which you turned to remove it. I tried crossing the o.e.m. part number on Napa's website but nothing came up. There was a gasket under the cap o.e.m. part number 080445 1 1/4" I.D. X 1 11/16" O.D. X 1/16" thick fibre, you might try doing a search on Ebay for those part numbers, hope that helps.
