Night Vision Rubber eye cup for older ITT 6015, without retaining ring?

[FORESTBARBER]

My eyepiece has no threads for the retaining ring. TNVC says there is such a thing as an older rubber eyepiece, that I suppose friction fits over the lens. I have googled the heck out of it but cannot find.
Any sources out there?

Thanks!

 

[compasscall]

Does it look like the one pictured below?



If your ocular looks like the one pictured, you'll need a threaded insert and eyecup ring as pictured below:







The threaded adapter ring is made by Adam Barker of ABNIGHTVISION

He's sold some via ebay: PVS 14 Eyecup Adapter Ring Set 25mm to 30mm Night Vision