Try this page for the rivet and washer size you need- buy the shortest brass rivet there:
https://model-motorcars.myshopify.com/collections/small-parts-hardwareThe instructions below assume you have the tools and dexterity to do them.
Fold a piece of paper several times and drill the same or slightly smaller size hole through the folded paper. Unfold the paper and cut it into strips with the hole at one end.
Snip a rivet to be long enough to get in and have two pieces of paper and the washer on top.
Slide the hole over the straight end of the rivet and add one TINY drop of oil to the paper. Feed the rivet through the two links. Add another TINY drop of oil to the top link hole.
Wedge a piece of styrene behind the rivet head, to keep it from falling out. Put another strip of paper over the end of the pin.
Place the washer over the end of the pin.
Carefully add a tiny bit of solder flux on top of the washer.
Fire up the soldering iron to the hottest is can be, clean the tip and add a small drop of solder to the tip.
Touch the solder on the tip to the washer, letting the solder flow, and quickly remove the iron.
Let the solder fully harden, and snip off any excess rivet. File the new "head" flat without removing the solder, which hopefully flowed into hole of the washer and onto the rivet shank.
Remove the paper pieces- these should have prevented the solder from fusing the pin to either link and provided needed gap for smooth movement at the joint.
Here is an an image where I did similar, difference being that I put the washer behind leaving the rivet head outward. Note that the plastic hangar did not melt from the quick touch of the iron: