Sites like eBay sell "COA stickers" or "digital keys" for $10–$30. While these might work, they violate Microsoft’s licensing terms. Additionally, because this is an Embedded edition, the keys are often resold from decommissioned ATMs, which Microsoft can blacklist.
As of 2025, Microsoft no longer sells Windows 8.1 Embedded Industry Pro licenses. The OS has reached end-of-life (EOL). However, legitimate keys still exist in legacy environments. windows 81 embedded industry pro product key