You can find replacement shells for both, Switch and JoyCons and replacement for USB ports on AliExpress. The seller also has lots of 3DS parts, and are expanding their Switch catalogue, so maybe they will the ones you look for in future. UPDATE: Digitizers starts showing up eg. here.
I ordered replacement shell for switch from AliExpress and didn't have time to install it yet, but judging by the looks of it, it is identical to the original. I can update you when I manage to install it.