Buy from Amazon.com : http://fave.co/1BM0hZO

Pentax AF540GZ II flash New Weather Resistant Flash Unit for Pentax SLR's with Case (Black)

Product Description :
Weather resistant All Weather AW construction pairs perfectly with PENTAX WR DSLR cameras
High Guide number for increased range and versatile flash performance
P-TTL mode with pre-flash allows for more accurate strobe photography
Constant light source for video or long exposure still photography High speed on camera and high speed wireless flash is available in P-TTL modes
Flash exposure compensation through a simple control dial LCD display shows the effective range of the flash