I'm unfamiliar with iPhoto, but if it's fully up to date and still does not list the Pentax K-M then see if it allows you to manually select the Pentax K-200D.
As the K-M is essentially a budget variant of the K-200D it may solve your problem.
If not, then hang on a bit longer and someone who is familiar with iPhoto may see your question and be able to provide a more accurate answer.
Answers & Comments
I'm unfamiliar with iPhoto, but if it's fully up to date and still does not list the Pentax K-M then see if it allows you to manually select the Pentax K-200D.
As the K-M is essentially a budget variant of the K-200D it may solve your problem.
If not, then hang on a bit longer and someone who is familiar with iPhoto may see your question and be able to provide a more accurate answer.