Pipe adaptor for water filter: 10 mm pushfit pipe to 1/2" or 12 mm (outside diameter) thread

We have a water filter similar to

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although ours is made by Blanco according to the paper label stuck on it.

The threaded adaptor between 10 mm plastic pipe (Push Fit) and the female thread on the filter housing has sheared off so we need a replacement.

But I'm struggling to identify the adaptor so I can order one online (since I can't really break lockdown). The threaded end is 1/2" or 12 mm outside diameter - between the read lines in

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The inside diameter of the threaded part is 9/16" (I know imperial for some godforsaken reason quotes inside diameters!) The threaded part should be inline with the black hex nut of the adaptor - as you can see it's sheared off and I've laid it alongside.

As far as I can tell, it needs a male thread - it doesn't seem to be a female thread with a separate male-male adaptor (half of which is stuck inside the nut).

I can find lots of references to 3/8" screw thread, but that seems too small to match the 1/2" (4/8") or 12 mm thread.

There was a slow weep from the filter which seemed to be coming from the inlet port. So I tightened it about 1/4 turn and the thing sheared off. I wonder whether it had already started to separate and I just finished it off.