Got a link? The Tri-State I found didn't list any MF equipment when searched for 300mm and Pentax. And I wasn't going to lift up and look under every link to find it.
When I went looking for my M* 300mm, I found places that listed it but when inquired they really didn't have it (old web pages, maybe). I ended up getting mine through
Japan Exposures an equipment sourcing service. The service was good and the used price was satisfactory after all the fees. My thought was I didn't expect bargain basement price for a hard-to-find in the US lens. If you lived in Japan, it looks like you could get one from Amazon of Japan.
A funny story about that. I inquired to Amazon of Japan and asked if I could order from there while trying to get that lens. They said, yes, but you need to create a new Japan account. They provided useful English links plus other helpful information. They concluded the e-mail with a list of things that could not be exported. The list was so comprehensive that, really, you couldn't buy hardly anything worthwhile!