There's a ton of different adapters already between edsff connector used for e3 / e2 / e1 drives and everything else pcie already (pcie, m.2, u.2). For example this pcie card. (Good luck tweaking your equalizer settings jumpers by hand though, whew!!) https://www.microsatacables.com/pcie-x8-gen4-with-redriver-t...

Drop that in one of the many usb4 to pcie docks and you should be good to go. Pretty fugly but it ought to just work! I think there's some cheaper models that are under $90 still available, but here's a listing. https://www.dfrobot.com/product-2835.html

I believe a more focused dedicated usb<->NVMe chip might also work, if attached to an edsff connector. I didnt look hard, but I haven't seen any such products yet, but: it's mostly mechanical/packaging, some signal integrity checks, but generally wouldn't really be much different in the end than a NVMe adapter. Seems very doable.

Build it! Someone could sell (to quote a Daily Show) literally dozens of said adapter! (Eventually probably many many more, but not a huge second hand market for edsff atm).

It needs to be portable/travel-friendly, something like this: https://global.icydock.com/product_327.html