thingiverse
An elongated cup with rounded corners that hooks onto something. My wife uses it to hold a phone on a treadmill. It prints sideways and has curved edges around the hole, so shouldn't need supports.
Made in OpenSCAD, so it should be configurable.
Instructions
I built mine with .2 layer height (it's functional, not meant to look great) in PLA on a MakerBot Replicator 2.
Direct link to the original creator's page
Click the "View on thingiverse" button above to visit the original model page on thingiverse. You can download the STL file directly from the creator's page for free.
This STL file is compatible with most FDM 3D printers (Creality Ender 3, Prusa MK3S+, Bambu Lab, etc.) and resin printers (Elegoo, Anycubic). Check the original page for recommended print settings and materials.
Yes, this model is available as a free download on thingiverse. Some creators accept tips or donations.
Most STL files can be modified using free software like Blender, TinkerCAD, or Meshmixer. Check the license on the original thingiverse page to see if modifications are permitted by the creator.