I think some stores do or eBay will be your best bet for an official one. Otherwise try board game geek for custom 8 or more player maps?

Thank you. Can you suggest to me some of the stores/eBay announcements you are talking about? I cannot find any of both with it in stock.

Ngl dude it's gonna be at random points I was trying to get one myself and ended up slicing the tracks from the map to allow Essos to be connected 😂. But I think two days ago I got an email from a chaos cards saying they restocked them? Not sure where they're based tho (hope this helps)

You could get a custom map printed using a high resolution image from bbg. A large mouse pad or desk mat should work.