Where can I buy Regal Aya in Warframe?

Excuse me, could you please clarify where exactly one might go to purchase Regal Aya in the game Warframe? I've been searching for a reliable source, but have had some difficulty finding a definitive answer. Are there specific in-game vendors or perhaps a specific platform where players can make such a transaction? Your expertise in the field of cryptocurrency and finance may not directly apply to this inquiry, but any insight you can offer would be greatly appreciated.