Back in my film days, I loved the central microprism of my K2, and hated the split image system when I was forced to replace my stolen K2 with an ME.
Here is the goto place (as I understand it) for replacement focusing screens these days:
https://www.focusingscreen.com/index.php?cPath=25&osCsid=4dc637eb6dbfeb324a0a3d2b74992640
If you do a search with the words "focusing screen" in the "search the forums" box near the top right of any Pentax Forums screen, you will see that there have been a number of threads on this topic,with the expected variations of preferences and experiences!!!
I have found my eyes now to be pretty unreliable using the standar clear focusing screens, with my experience of the K50 and now the KP., and am teetering on the edge of ordering the Ec-A Focusing Screen (with central microprism) that worked so well for me in the middle-late 1970s with the Pentax K2.