Integral 256GB USB3.2 Type-C Ultima Pro X Portable External SSD - 2000MB/s £34.99 @ MyMemory

I may be a little sceptical but as I just got a laptop with TB4 in then I should be able to get the full speed out of this.

Can't find any real reviews of thsi but 3.2 2x2 is a 20Gbps link and even just a drive case is over £50. Worth a punt to see I think.

Will report back when it has arrived.

Reading up it may be that TB4 and USB 4 will treat USB 3.2 2x2 as the slower 10Gbps speed. I'll confirm when it arrives.

The drive arrived today. It is quite low profile and much smaller than any 3rd party external NVME case I have seen. It comes in a little carry case with the two cables.

Performance on a Thunderbolt 4 port on my laptop is at the lower USB 10Gbps speeds. I ran a Crystal Diskmark on it using a 64Gb size so this would be the worst you could expect, and it shows that the speeds don't drop off with large file transfers (eg 64Gb). These results would be the same for USB 4 as far as I can tell. (edited)