https://www.makerbeam.com/makerbeamxs/xs-5x5mm-black-profiles/
MakerBeamXS - 5x5mm - black - MakerBeam
With 5x5mm in diameter XS profiles are really small and also very lightweight. They are available in blue, clear and black. Bolts and nuts are M1.2 size.
makerbeamxsblack