Originally Posted by k10dbook 
Two types of adapters are available, all available on Ebay or camera stores. I believe Pentax does not manufacture them anymore. One type allows for infinity focusing and the cheaper doesn't. See link below for more information.
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I ordered a brand new M42 to K mount adapter directly from Pentax a few weeks ago. I called Pentax Colorado and the guy was very nice. He said he didn't know when they would have some in. I gave him my credit card info and hoped for the best. I got the adapter in the mail 10 days after I spoke to him. I say give Pentax a call and see what they can do for you.