Afraid not from what I could find on the usual sites. Nothing on ebay UK, Scan UK has it listed as EOL and there is one on Amazon for almost £150. At that cost I would rather buy the Fractal Design Meshify 2 XL.
Only Cool Master 400 cases I can find for sale are the NR400 or the S400.
Did you manage to find a case in the UK? I was looking at the v5 NAS and found your post, and I think the bundle you have so was going to copy your plan!!
If you haven’t found a case, I will do some digging as well.