UPDATED 3.5.2023: Improved fitment

Print wide base touching the build plate, supports “Touching buildplate” so the plunger get's supported.

I used eSun PETG Solid Black with 0.2mm layers, 8 walls (or whatever fills the whole space).

I've included another model that has some grippier texture on the sides, you could also just attach some glue-on grip tape or stipple it with a soldering iron.