Have you tried Pressure Cooker Outlet?

They have quite a few pressure canner parts and, if they don't have them, they may know where else you could look.

They were very helpful recommending parts for our old World War II era pressure cooker, and I got them quickly for a reasonable price.

Presto at gopresto.com also offers all the replacement parts including the screw in valve and the 3 piece weight set for conversion. If you prefer to use the All American valve and are sure it will work, it is available from the manufacturer as well.

Dave

I just did this to my Magic Seal 16 qt model. This was a Wards model like the Sears Maid of Honor series, but they were all made by presto. I bought mine from pressure cooker outlet listed above. The part number of the outlet fitting is 1058. That replaces your older version and it screws in to the threaded hole in the lid. Easy does it as to much force will strip Aluminium threads. I used Teflon tape on mine, just like plumbing. I also bought the 3 pc weight set. I also found the outlet on ebay $9 shipped. My gripe with the PC outlet $9 shipping which made the total $30 for the outlet and weights. I still love the older machined PC's and these upgrades make them run like a new one. Hope this helps.

Larry