barkdog––
My PSL also came without the rubber eyepiece. I called Classic Arms (the supplier we ordered it from) and they sent me one with no argument, in three days. I expect that most distributors would do the same, but, barring that, call Century International Arms (the importer) at 800-999-4899 or 800-270-2767. Century will also send you a manual (PSL 54-C Rifle) free, if you didn't get one with your rifle.
If none of the above work out for you, check with Natchez Shooters Supply (natchezss.com); the have very similar rubber eyepieces in the Dvorak brand. Good luck!