You may consider the older DA18-250mm/Tamron18-250mm. It is not OS and does not have HSM. It is discontinued but you find it regularly on the PF marketplace and Keh.com listing for $350-$450.The Tamron tends to go slightly cheaper, but the two lenses are absolutely identical.
The lens is very sturdy. Definitely. And it was tested by many Pentaxians here and elsewhere. The iQ is regarded among the best among all brands' superzoom lenses, but it not on par with a prime lens.
The lens weights 45g, it is pretty compact when at 18mm. There are many worthwhile user's reviews at
SMC Pentax-DA 18-250mm F3.5-6.3 ED AL [IF] Reviews - DA Zoom Lenses - Pentax Lens Reviews & Lens Database.
My wife and myself share the DA18-135mm and DA18-250mm. My wife likes the DA18-135mm and I prefer the DA18-250mm, but the IQ is very similar between the two lenses IMHO.
I shoot mostly outdoor in all-weather conditions, incl. storms, rain, sandy/windy conditions. The DA18-250mm is perfect for my needs, as long as you take care of the zoom (to avoid pumping droplet in).
I hope that the advice may help.