The Japanese store Yodobashi Camera has some useful pages that list all available lenses for Pentax systems.
What I like about these lists is that they show not only the Pentax lenses, but also the main third party options. I haven't seen many sites that lay all the options out so clearly.
in addition, many of them have reviews with some quite nice photography, especially the ones by Toshiki Nakanishi. You can see the ones with the reviews, because they have a grey lozenge with レビュー written on it. Where they have a review of a third party lens, it is actually with a Pentax camera. Don't expect too much critical evaluation of the lenses in the reviews; this is a shop after all, and the main purpose is to fuel LBA.
Here are the links.
Wide-angle zooms -
PENTAX?????????????? ?????????? | ???????
Standard zooms -
PENTAX?????????????? ?????????? | ???????
Telephoto zooms -
PENTAX?????????????? ?????????? | ???????
Super Telephoto - zooms
PENTAX?????????????? ??????????? | ???????
Wide-angle primes -
PENTAX?????????????? ?????????? | ???????
Standard primes -
PENTAX?????????????? ?????????? | ???????
Telephoto primes -
PENTAX?????????????? ?????????? | ???????
Macro lenses -
PENTAX?????????????? ???????? | ???????
Anyway, I hope they are of interest to someone.