I have one on my k10d off ebay sent from Hong Kong.
I chose it over the original Pentax for two reasons:
1. It holds two extra batteries, which makes a total of 3 incl the body's (for 1 month travel in Europe taking about 3500 shots, I charged once.)
2. It has a position for putting the strap on both side bottom. So, I ended up putting the strap on the top left strap holder (on camera) and bottom left strap holder (on grip) and tied a knot on the strap and made it work like hand strap.
and it was half the price over the original, + a shutter on each side....
Althought I knew the original have weather seals + dial + green button which the generic one doesn't.....
Whatever your pick, with grip is better than without!
Here it is on my k10d