Inspired by Japanese antique 矢立(Yatate) portable drowing set.I designed travel brush fit inside hole.Davinci pocket brush #2 and Escoda travel brush upto #4 fit in the hole.
The hingen shaft hole is 1.8mm. You can use filament piece for FDM printer.Two magnets can be set to provide additional friction of opening top cover.Magnet size 4mm X 1.5mm