Master Brake Cylinder Cap Gasket
 

I am trying to find the Master Brake Cylinder Cap Gasket... Here are some photos of the van.
Anyone know what part number it would be?
I am trying to pass inspection and need to replace this part.
https://photos.app.goo.gl/gZmm8N8yRbG8vySj2

Model and year might help.

Not an express or savanna.
Maybe an old G van.

May need to hit up and auto wrecker.

Sorry, is a 1995 Chevy G20
This is the actual part that I need, which is proving difficult to find: Brake Master Cylinder Diaphragm - Oshkosh Equipment
Might have to get the entire Master Brake Cylinder box.

RockAuto says this will fit: 1995 CHEVROLET G20 5.7L V8 Master Cylinder Cap Gasket | RockAuto, probably the second one of the three.

Thanks for the reply. I actually bought the mentioned part from Advanced Auto Parts, #42103, and it is too small.
The box that holds the brake fluid is quite large, measuring about 6" x 4".

That doesn't seem like the original master cylinder for that van. Most G series vans have a plastic reservoir with 2 compartments. One shallow one deep.