another need i could not find in the community, so i struggled through fusion 360 using the gridfinity add-in plugin and came up with this. it hold my 81mm alcohol dispenser very nicely with .5mm clearance on all sides. i covered mine in plastic wrap cause i'm not sure how abs reacts to alcohol long term.

I hope this hold your 81mm circular object just as well as it did mine.

No need for supports! This model is still stackable as per gridfinity standards!