Someone said he would like a 300/2.8 in a recent thread, here :
Sigma EX 300mm F/2.8 Lens For Pentax | eBay
One of the best fast zooms made by Pentax (some say only 1000pcs ever made) :
Pentax SMC P FA 80-200mm F/2.8 Lens | eBay
Hard to find as its discontinued on K-mount
Sigma EX 180mm f3.5 Macro APO IF - For Pentax 085126105457 | eBay
Sigma EX 300mm F/2.8 Lens For Pentax | eBay
One of the best fast zooms made by Pentax (some say only 1000pcs ever made) :
Pentax SMC P FA 80-200mm F/2.8 Lens | eBay
Hard to find as its discontinued on K-mount
Sigma EX 180mm f3.5 Macro APO IF - For Pentax 085126105457 | eBay