my dad have this thing:
He owns a more modern version The Bellows II, manufactured by honeywell-pentax instead of asahi-pentax,
He bought it like 30 years ago for use it with a spotmatic, and it can be used with the k mount with a couple adapter rings.
He is making some adapter rings for use it with my 40D, of course the lens will have to change, as it is a cropped frame model.
He also have a Hama Dia-Duplikator:
This one is even more simple, screw a t mount on the camera and just screw it onto the barrel!
Works with all brands of camera, and the barrel has this selector of your crop factor.
The last one is at 17 eur in ebay