I know, how helpful are little nuts, bolts and screws. I also know, that it is really problem to prepare something like this with diameter below 0.5mm. I've got a lot of this prepared for my models. Four of them I've prepared as a commercial products.
It's:
screws 0.29mm, 0.35mm and 0.42mm
hexagonal bolts and nuts on washers 0.45
see it below both mounted in the model and as a commercial sets:
Do you think it's a good idea? I can prepare a lot of diverse types bolts, nuts and screws (I've it prepared for my own use).
All the best, Lukasz