This is the last one from me about tiny bolts/washers. There was a great Scale Hardware company number of years ago, went down and - yesterday, I learned they are still around, different name. Check this out: https://model-motorcars.myshopify.com/collections/small-parts-hardwareNo, I did not order yet. I'll do some experiments first. I do not have any 0.2 mm brass plate in da house but I have 0.1 and 0.3 mm. I'll try to cut a 1x1 mm piece of each, drill a 0.45 mm hole in both and see if it is possible to squeeze a small 0.5 mm brass pin through the hole. Alternatively I'll buy some 0.4 mm brass wire amd try how much head size it will make to "cut"it by rolling it with a 45 degree edge. For different reasons it will take some time before I can make such experiments but I guess it will also take months before I get to this point of the build.
I noticed RB Motion also sells button head brass pins but that way will also be rather expensive (almost unbelievable BTW that they also have hexagon bolt pins and nuts where the diameter of the hexagon is only 0.63 mm)