Originally posted by jawats (1) 13" laptop and charger
Almost every bag will be ok.
Originally posted by jawats (2) Pentax K-1
Same.
Originally posted by jawats (3) Pentax 150-450mm
That's by far the trickiest requirement. For this long lens, I have to disqualify the Mindshift Gear rotation180, they can't accommodate it, except maybe if you're willing to get their top insert. Even then, we'd have to measure I'm not sure it fits.
Originally posted by jawats (4) Pentax SMC-F 50mm
(5) Sigma 24-70mm IF EX DG HSM
Easy peasy.
Originally posted by jawats (6) Basic first aid kit (6" by 4")
(7) Athlete water enhancers
Same.
Originally posted by jawats (8) Water bottle
Most bags have an external pocket for this. Several also accept water bladders.
Originally posted by jawats (9) K-1 battery grip
No problem there.
Sooooo... regarding that long lens.
One avenue is to get either a Nomatic MacKinnon or a Peak Design travel backpack, and with the proper insert configure the interior properly. In both cases you'll have some room left for the rest. But these bags are not truly meant for hiking.
another option is a Peak Design Everyday Backpack 30L, and place the lens vertically on one side thanks to the adjustable dividers. I've done something similar often and loved it. With the optional hip strap, the bag is comfortable for 1-day hiking.
Another avenue still (with bags I personally haven't used) is to go full-fledged multi-day setup with an Atlas or a Shimoda bag. You'll have to measure up stuff but clearly these companies should have a bag which fits that lens. Same for F-Stop. The price will scale quickly however.
Another yet, Mindshift Gear offers some bag (the UltraLite I think?) with full internal organization for photo gear. Again, configure it properly, and leave some of the volume for non-photo stuff.
These suggestions should get you pointed in the right direction.