With TradeSkillMaster Premium, you can search for any item that would appear on the Black Market Auction House via the TradeSkillMaster website.

In the following example, the item is currently listed on two US realms and one EU realm, while Ravencrest EU is set as the 'home' realm from the selection dropdown in the top right:

Below this results page, you can also enable and manage notifications for the item on the Black Market Auction House. The Region specified matches the region of your 'home' realm from the selection dropdown in the top right.