The more I look at Dawn's photo and your machine (although even magnifying it having a hard time seeing what I want) the more I think a 66 slide plate would work. Some of the online machine parts places are out of stock. There are several on Amazon
https://www.amazon.com/s?k=32569+slide+plate According to one of the Amazon pages says the Plate measures approximately 2-1/16" X 1-13/16". They are kind of fiddly to install, but the instructions are on the lower right of the page of the 66 manual at
https://www.manualslib.com/manual/12...?page=6#manual.