Gottlieb used a couple different doors in the ’70s. Older games all featured the 1962 door. Starting with Spirit of 76, near the end of the EM pinball era, their multiplayer games used this door, and all the solid state games used it. It appeared in both a plain metal style (System 1) and a textured style (System 80).
Like everything Gottlieb made in the ’70s, these are pretty much tanks. A few parts are available from Pinball Resource, although there are lots of donor games to steal from. I particularly like the System 80 style as it doesn’t even show fingerprints. The stickers are frequently damaged, but PBR has them available.