Kenko 2X MC-7 teleconverter with Pentax cameras.

I have a Kenko MC-7 teleconverter, It doesn't autofocus with DA* lenses, but it does autofocus with my Sigma 105 f:2.8 macro lens and my Pentax 12-24 f:4 wide angle zoom. It also works with my D-FA 150-450 lens, although it doesn't always "nail" focus on the first try, probably due to the rather small lens aperture, especially on the longer end of the zoom range. However, what is interesting for me is the "preset" option of that lens, which work flawlessly with this lens/converter combo. It comes in real handy while trying to photograph birds flying in and out of their nest/habitat. There is some loss of sharpness, but being able to get "the shot" is an acceptable compromise to me.

Any other lens/converter combo you know of that works acceptably wel with Pentax cameras?

i have Kenko Teleplus Pz-AF 1.5x MC DG, it has the Pentax SDM / Sigma HSM contacts which yours lacks. Later versions should be the same but you would need to check. Do not see this version come up 2nd hand very often. There are the Pentax teleconverters but very expensive which i believe the later Teleplus ones have become also.

i have the kenko pz af 1,5 dg works with screwdrive and sdm and also the tamron pz af 2x quite offten
use on my sigma 70-200 2.8 with good result,s

The Kenko MC-& has the contacts for SDM. It would not focus the 150-450 without those.