All I have ever seen advertised come with the trunnion, never seen them separate. If you can come up with the approximate size Fastenal or Mcmaster Carr should have something useable.

 

kernel,
I looked at mcmaster carr for the rivets the only ones they have are brass and copper flat head that are used in HVAC units. I guess I could get some rounded head rivets and file a flat spot to hold the barrel. muttman