Doesn’t appear so on the website. It’s not available on any region.
On aside note, the link in the announcement doesn’t work because it uses the old Battlenet URL system, so it not working is to be expected. Any links that use the old system will 404.
There are a lot of items that aren’t available to purchase on the shop website or only available there in bundles.
If you go into the SC2 client and go to the Collection tab you can find most of these and purchase them from within the game.
I checked and Nathanias is still available to purchase through that tab. Others who can be purchased in-game but aren’t listed on the shop site are Vorazun, Pomf & Thud, Day[9], and Park.