One option, if you have a reasonably low student-to-instructor ratio: make it an oral 1-1 exam for each student. A video call with the instructor and the student; you ask questions, they answer. If you have 20-ish students, it will eat up half a work-week or so, which is more work than grading 20 exam papers, but not _that_ much more.

Of course if you have 50 students per instructor this is not going to work...