I think others might be able to answer better, but I know in my own case... you just have to look elsewhere when a manual isn't in the AW library.
The ephemera section is bursting with a lot of helpful texts, but I believe most of what exists in it came from private collections that volunteered to donate them to the site to be scanned, as well as (possibly?) public domain scans. So every vintage appliance manual isn't covered for that reason.
But, here's some tips I've tried.
Look here on the site in the forums: Sometimes members have answered questions about an appliance, that wasn't covered in Ephemera, with a few scans or quotes from their own privately owned manuals, So many awesome people on here have answered so many questions and offered help that the forum is almost like a manual itself.
Again, here on the site, try posting a Looking to Buy message in Shoppers Square. It's possible a collector may have an extra one to sell.
eBay can be helpful. The chances of finding what you need right off the bat are very slim, but, choose the 'save this search' option and eBay will email you in the future if what you are looking for ever does show up. Check Etsy and other similar auction sites too.
Less likely but FB Marketplace and Craigslist might help.
Internet Archive: Many books and manuals have been scanned and saved here, it's worth a look
Google: enter the manual / appliance name you want and add the term PDF, Download, or Ebook (or similar) and you will likely get some hits, BUT be very cautious, as you will most certainly get scam sites as seemingly legitimate choices because manual searching seems to conjure those up.
If you do find any that aren't available in the AW library you might consider donating them to be scanned, I don't know for sure with the sites new redesign, if it's still an option, so ask the Ephemera Librarian first of course.
This is a pretty cool place, I think you'll like it here.
