I've seen some various designs but wanted one that was slim and fit well for my specific stroller!
It uses a keyed interface between clamp and mug holder so should be pretty sturdy! If the flat head screw keeps getting loose just put some superglue on the threaded (3d-printed) plastic before you tighten the screw fully as thread lock.
It uses 3 pieces of hardware:
I uploaded my fusion file so you can change the hole specs if you want to use other fasteners. Should be fairly easy to change to fit other strollers as well!
The author marked this model as their own original creation.