Source for replacement "seals" / "Gaskets" for Mamiya C330 focusing screens

I have two C330 focus screens and they rattle within the metal frame (screws are all tight).
It seems that the seals / gaskets have lost their ability to hold the actually screen in place.
I see that US Camera has a product for C330F focus screens but not sure they would be the same as for the C330 focus screens I have.

How do you tell a C330 focus screen from one for a C330F?

Any advice or feedback would be great.
(I have reached out to US Camera but have not heard back as of yet)

Thanks

Todd

330 and 330F screens are the same. The 330S has a different screen.