JAK wrote:
There's a K-01 for sale on the forum here:
https://www.pentaxuser.com/forum/topic/f-s--pentax-cameras-and-lenses--mz-s--fa-...
That camera is also listed on Ebay at a higher price where it is cunningly disguised as an M42 standard lens. Just goes to show how scarce they are that sellers have to disguise them!

JAK wrote:
K-01's are scarce because they were only available for around 12 months from Feb 2012 to Feb 2013.
As you are asking about is it any good or popular I'm wondering what you know about it. It isn't a DSLR so those who like a proper viewfinder aren't catered for. Some didn't like the 'brick' design of it and control layout making it uncomfortable to use. But it shares the sensor and general workings of the K-5 so it produces fine images.
It was a controversial camera which some liked and some hated. I guess it didn't sell well, stocks were sold off at half price and then it was discontinued which has made it something of a collector's item.
I'd read some reviews to see if it is a camera you'd love or camera you'd hate. I can't answer that for you!