The K-5 cases are available on EBay and HiFiDo (under Accessories but be quick to pounce) and you can sometimes find the 10 cartridge holders which were made by the company that originally made the K-5 for Fidelity Research.
The internal foam is very rugged if it hasn’t been abused.....
HERE
The internal foam is very rugged if it hasn’t been abused.....
HERE