They don't exist because of FFD and other factors.
You can go from Pentax _> Canon, but you can't go Canon -> Pentax.
https://en.wikipedia.org/wiki/Flange_focal_distance
"The Canon EOS mount is larger in diameter than the Pentax K mount, which is why you cannot physically mount an EOS lens to a Pentax camera. But the reverse is true. Beacuse the Pentax K mount is smaller in diameter than the Canon EOS mount you can use an adapter to mount K mount lenses on an EOS body"
https://www.pentaxforums.com/forums/10-pentax-slr-lens-discussion/10502-adapt...ns-pentax.html