|You have a bunch of options:
Pentax AF360FGZ - Earlier model, has tilt, but no swivel. Slightly pricey (around $299 U.S.), but very decent. Supports front/rear curtain synch, High-speed synch and zoom. Also has many smaller features.
Pentax AF540FGZ - Latest model, has tilt and swivel, all the same features as the 360FGZ, higher guide number. Very pricey.
Pentax AF-200FG - Very basic flash. No tilt or swivel, meant as a travel/portable quick flash.
Sigma EF-500 DG Super - Flash much like the 540FGZ, smaller guide number (I think), cheaper in price. This flash also comes in a couple of lesser models without high-speed synch and other features. Watch for that.
Pro-Master 4800XT - Doesn't support high-speed synch. Cheaper model, hard to find sometimes.
There are others.. Sunpak makes a couple of Pentax mount flashes, but none with the more advanced features.
Just keep your eyes open and look around. Personally I'd recommend the Sigma EF-500 DG Super if you're looking for a good full-featured flashgun with a decent price. All recent Pentax DSLRs fully support it