vacuum pump internal parts valves 300SD engine

[rhodes2010]

I searched but found nothing on this:

My 300SD engine vacuum pump had I think 3 plastic one way valves
inside the pump last time I took it apart.

In my observation all that was wrong was the plastic valve finally disintegrating.

When I look at $300 rebuild kits I do not see the little plastic one way valves.

The other option is the $400 pump in complete form.

I will likely start scavenging junkyard pumps for these internal parts.

I did check/install the one way valve that is inline and is metal outside the pump.

Does anyone here know or agree with what I am describing ?
The plastic one way valves that allow the pump to actually pump and hold vacuum.

So why can't we purchase these valves alone by themselves ?