I'll try and help, but details might be fuzzy.
The K9 knives were a joint project he started with Dan Koster, in addition to both of them making their own knives. I do know Tom Krein got super busy with his own knives and finally closed his books to orders. Occasionally I'll see some K9 knives up for sale over at USN where there is a subforum for Tom Krein & K9 knives, but not often. Not sure what level of involvement Dan Koster has in K9 anymore.