As another user stated Startech makes one and I use it as a technician. It's not fast at all... it's mainly for recovery when you don't have a motherboard with an available M.2 slot you can still pull the data off it.

For that purpose it does the trick. The drive is capable of speeds 100x above USB 3.0 so there really isn't good to use that bus for anything other than emergency.

- Here is an image of the circuit it uses (ASM1163E Controller) https://i.imgur.com/ZmwppR4.jpg

- I can't find that IC anywhere but here's the closest thing: http://images.100y.com.tw/pdf_file/35-Asmedia-ASM1042A.pdf

PCI-E to USB 3.0 host bridge. Hopefully that helps.