I found the fingerprint readers on many laptops are internally connected via USB interface, so decided to get one and mod my keyboard to include FP reader to allow Windows 10 Hello login with fingerprint. First try was a FP reader from HP ProBook 6440B (VFS451) - unfortunately, it wasn't accepted by Windows 10, but it worked fine with Windows 8.1 . Next one was coming from HP Pavilion DV7 (USB\VID_138A&PID_0018) and despite more difficult wiring, I was able to connect it via USB to test, and voila, was working fine.
Next step was to pick some small USB 2.0 hub and use its internals. Ali suggested really cheap one (https://www.aliexpress.com/item/32948220421.html) and after long time of waiting and final disassembly it turns to a perfect choice thanks to its small dimensions. I disassembled the keyboard, solder cables and make a POC (proof of concept) with great result - working as expected. Next part was the more difficult, to cut appropriate hole and fit all inside.
I had to cut PCB to make it as small as possible, taking care to NOT cut Vusb trace. First cut kept pads for USB sockets, but later found it still too big to fit into keyboard. Second cut was right next to chip pins, luckily the chip HS8836A had all "output" D+ and D- pins on a one side of a package. Then I solder wires and pack whole hub PCB into Kapton tape and cut appropriate hole in a middle panel of a keyboard. That one is covered by a grayish part, so no need to cut it precisely. To save some precious space, I've also removed original connector on a keyboard PCB and solder wires directly.
Last step was drill and grind the slot into gray top cover. I've marked slot with a permanent marker, drilled some holes and used small rasp to make a final size. Then using a dremel with small grinding bit I had to make a gap from a bottom side, to allow FP reader protrude from a plastic cover. That turned out as most challenging task, because grinding made plastic melting and was easy to screw it up - and I did it a bit. As a last step, I fixed FP reader with glue gun and mount all together.