Part Identification

Could someone help me identify the caps that are used in the two photos below? There's no way I can justify paying $170.00 for this thing. If you're interested, these are "hydraulic wet cleaning machines" for LPs / records... and people are paying that price.

The first picture looks like the used two 4" PVC cleanout plugs... however, they do not appear to be threaded AND they somehow installed o-rings on the underside of each plug.

The o-ring is much more visible on the second photo, but I have no idea what type of cap they used. Could it be a 4" cap that they simply cut on a band saw?

The key here is the o-ring. The label of a record / LP is 4" wide. So, whatever it is, would have to be sandwiched between two 4" caps (or whatever) with an o-ring between each one. The goal is to create a water-tight seal between both sides of the record so the label remains dry while it's being washed.

 

This thread looks like an advertisement to me.
I removed the links as they did not have anything to do with your question.

 

You could certainly mill a groove for the o ring into a PVC cap on a milling machine. But a 4" PVC cap would be more like 4 1/2 inches OD.

It would be a perfect candidate for 3D printing.

 

PJmax: Not sure why you'd think this thread was an advertisement... especially since I'm outright stating that I think the thing is highly overpriced, a waste of money, and could probably be built for around $20. I'm just here hoping some plumping folks could help me identify the pieces used in the pics so I don't have to shell out hundreds of dollars for the thing.

BTW: I included the links so that someone on the forum might be able to see the potential and make some cash by building / selling it themselves.