The latest products to hit the virtual shelves are teeny. There is now a choice of 3 different size of split ring, intended for 7mm & 16mm Scale tie-down and horse links etc. The sizes are 2.3mm I.D x 0.5mm wire and in 0.64mm wire a choice of 2.7 or 3.2mm I.D. I’d be happy to hear your suggestions for further sizes of these very useful items.
Then there are some scale-independant items. Socket Cap (Internal Hex or Allen Key) type screws in M1.4 and M2 sizes for small motors. These are particularly suited to attaching things in awkward spaces where an allen key gives a much better hold on your tiny screw, with less chance of it paying a visit to the carpet or floorboard gap monsters. Available in packs of 2 or 10, with further variations on the way!