I would search for "Pentax Attachment Lens" or "Pentax Attachment Lens 45-125".

Phil.

Thank you! Is there some writing on the lens in particular that I could enter in to Google or ebay in order to find the attachment lens? Thanks again.

Hi Mark:

I replied to your post, hope this helps. Phil

The Pentax close-up lenses are meant for prime lenses and are not designed for the K45-125/4 zoom.

What you are looking for is a dedicated "attachment lens" labelled 1:4/45~125mm

I don't have one and I've never see one for sale, but I'm sure they exist.

I do have the attachment lenses for my two K85-210 zooms if you want an example.

Greetings! I was informed that you are the 1970s Pentax expert. Perhaps you can help me with some info on this lens. HERE is the thread. Thanks!
Mark