Typewriters are an expensive and niche item these days, due to no longer being manufactured, and the good ones being collected by weird nerds. Sort of like buying a 40-year-old vinyl turntable that is in good and usable condition.
If I build you a custom device that receives questions from a central computer and lets the user plug in whatever keyboard they want via bluetooth or usb to only type and answer the questions (ability to edit the text and submit when ready). The central computer can receive all the questions submitted to any of these devices connected to it via wifi or cloud. How much would pay per device? Would you pay for a subscription?
I think this can already be implemented through a fairly mundane thin client approach, such as Dell/Wyse type thin clients, citrix stuff, or an ordinary x86-64 desktop PC setup with an absolute barebones OS that connects a graphical desktop session to something centralized over a LAN.