Update 5 February 2017: There’s now a second part of this, featuring some newer Pentax cameras.
1) Pentax shutter sound: Z-1P, K10D, K-x and K-5
2) Pentax shutter sounds: K-x, K-30 and K-5
3) Pentax K-5 IIs shutter sound
4) Pentax K-5, K-7, K10D and *istD shutter sounds:
5) Pentax K10D shutter sound:
6) Pentax K200D shutter sound:
7) Pentax 645D shutter sound:
Now for two that aren’t SLRs.
8) Pentax K-01 shutter sound:
9) Pentax Q shutter sound (lots of background noise!)
Youtube has many more, for instance similar samples from various additional Pentax film cameras, and of course from other manufacturers. Enjoy!