K10D Flash

Hi, am back into photography and using a K10D, have been suprised at some of the results in can produce. But I am short of a flash gub in my kit, I woild love a Metz or a Pentax 540 or 360, but thet pennies just wont get close. So can anybody suggest a third part unit that I can use indoors and outdoors on the K10D.

Thanks Andy

Im no expert by ant stretch... But for P-TTl I would look at the Sigma ST610DG or Manual flash the Youngnuo Yn560iii