I am trying to make some Thai style music in Music Maker with one of their native instruments, a khim. (example here: 
I hear it is similar to a Persian Santur, Koto, Hammered Dulcimer or Cimbalom. When searching for the instruments in the store nothing comes up. Is one of those available in a package of instruments?
@RoyalAssassin3 You can buy a sampled Khim instrument here: https://www.soniccouture.com/en/products/p265-kim/
You also need to download Kontakt Player from Native Instruments here: https://www.native-instruments.com/en/products/komplete/samplers/kontakt-6-player/
Kontakt Player is a free sample player and can be loaded as a VST (virtual instrument) inside Music Maker. You need Kontakt Player to play the Khim instrument.
If you need rare instruments for your music it is the best idea to search the internet for Kontakt sample libraries. At the moment Kontakt is the most used sample player in the music business. You can get nearly everything for it. But be aware that many sample libraries need the full version of Kontakt which is very expensive. The Khim instrument linked above only needs the free Kontakt Player, not the full version.