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Not Dead Yet: WD Releases New 6TB 2.5-Inch External Hard Drives - First Upgrade in Seven Years
(www.anandtech.com)
This is a most excellent place for technology news and articles.
Looks like this one except that it is sealed on one end and the caddies for the two drives have a cover plate that screws in over a gasket and rubber ring.
I got it in a shop in Hong Kong when I was there for a convention earlier this year. No idea if you can find it online, maybe somewhere like Alibaba.