See if you can find the missing part in the parts manual. This is a website that has manuals for download, FREE. PDF links are on the left near the bottom of the webpage.
http://thefeatherweight221factory.com/page7.php
Identifying the part makes it easier to find a replacement. I have some vintage part dealers you could try -
Glenn Williams -
http://pages.suddenlink.net/joyof301s/glenn.htm
I've sent him emails with the part numbers and even the reference in the manual and he's reasonable.
Can't find the one in Kansas at the moment, but I bet Glenn will have what you need.