I have one but unfortunately it is needed.
I can say that I can't believe that I ever lived without one. If you have to cave and buy one new, it will be money well spent. Tangerine is an awesome resource for the 914 community.
Wishing you luck in finding used one though!
FYI -- There are two types one is on a drop in type and the other accepts a larger screw to hold it to the jack while still allowing the plate to rotate. You'll need to note which type you need for your specific jack.