The Pentax AF200FG is quite similar to the Nikon SB-400 in size and features. It does PTTL exposure, but does not have certain advanced features such as HSS and wireless operation. Check the reviews, it's right there. Unlike the Nikon, which typically sells upwards of $250 new/$150 used, it sells for $80 new. I got mine used for $30. You can't beat the great value and pocketable size.
There are some older Pentax flashes that work in manual mode with digitals that might serve too. The AF200T (tiny) or AF280T (tilts and swivels) are good.
Last edited by slowhands95128; 01-09-2015 at 06:44 PM.
Reason: more suggested flashes