A year ot two ago, someone "found" a K1000 with a motor drive and a bulk film back.
https://www.google.com/search?q=pentax+k1000+motor+drive&biw=1430&bih=926&tb...h8ylvbwx8J4%3D
I don't know if Pentax actually ever made this as a product. However, the K1000 is basically a Spotmatic with a bayonet mount, and they did offer a Spotmatic Motor Drive. During the Honeywell years, one could send their ordinrary Spotmatic back to Honeywell, in Denver, and have it converted to a motor drive. The parts for Spotmatics and K1000's are largely interchangeable, so it wouldn't be hard to do.
Other than that, the only attachments available for the K1000 were a right-angle eyepiece and perhaps replacement focusing screen (the K1000 SE had a different one).
Then, too, you could always use the standard accessories that were not specific to the K1000, such as bellows, extension tubes, copy stands and filters. There were also microscope/telescope adapters.
There were a few third-party accessories available, such as slide copiers, but, again, there were not K1000 specific.