Where can I buy a SHx stronghold?

Could you please clarify where exactly one could purchase a SHx stronghold? Are there specific online marketplaces or exchanges that specialize in this type of asset? Additionally, what kind of verification or identification is required when making such a purchase? Furthermore, is it possible to negotiate the price of a SHx stronghold, or are they sold at a fixed rate? Lastly, are there any risks or precautions I should be aware of when investing in a SHx stronghold?