Where can I buy MOC in GTA Online?

I'm curious to know, where exactly can I purchase MOC, or Mobile Operations Center, in the popular game Grand Theft Auto Online? As a gamer who's always looking to expand my arsenal and enhance my gameplay experience, I'm eager to learn the best avenues for acquiring this impressive piece of equipment. Is there a specific in-game location or vendor where I can find and buy the MOC? Or are there certain missions or challenges I need to complete first in order to unlock the ability to purchase it? I'm all ears, ready to dive deeper into the world of GTA Online and expand my horizons.