Parts are readily available online but exact ones for older machines may be harder to come by. It appears to me what's missing is the height adjustment (Dial-A-Nap?) knob. I'm not sure what it would look like for that particular model, possibly a knob with a backing plate. To get an idea of exactly what you need, I'd suggest doing some Internet research to find a photo of one that is intact. The nice thing about those Eurekas is the design changed very little over several decades so there are tons of compatible parts across multiple Eureka and Sanitaire models, so even if you don't find the exact thing, you can find something that works. Someone has already done this with the Sanitaire bag on that machine. You can easily make it whole in the sense of being fully functional, even if it isn't exactly as it left the factory.
