Where can I buy a lens cover for Pentax 6.5x21x7.5 binoculars?

[BigMackCam]

Welcome

If those are the Papillo "pocket" binoculars, I don't believe they ever cam with lens covers - and, looking at the design, I can't see that any third-party generic options would fit. You'd probably be best off keeping them in some sort of pouch or bag...

[dms]

Mine (purchased new) did not come with one. Actually a rubber band and some thin plastic/cloth should work fine as the circumference is pretty constant on the objective lens end, after the first 1/4."