LifePixel seems to be popular for IR conversions but I am not sure they work with Pentax.
When I was researching about getting an IR converted body, I also looked into Spencers Camera and Precision Camera who both claimed to do Pentax body conversions.
Eventually, I went ahead and bought a full spectrum (clear glass) converted K-x from "lianglunche", a PF member who converts Pentax bodies and others overseas.
I'd Google for Pentax IR conversion. Also search here on PF as I remember a few threads with a similar question.
https://www.pentaxforums.com/forums/pentax-dslr-discussion/3344-pentax-ir-conversion-2.html
Also see Flickr discussion in the Digital Infrared or Converted Digital Infrared Camera groups.
Good luck.