Joby Gorillapod SLR camera head
This works with a standard 6 mm camera tripod threading. the hole where it goes through is designed so that you could self tap a thread in making it a stronger hold.
it is also designed so that you could print it without supports. it wont look great on the bottom however it does work.
I was able to print it in PLA however I would print it in PETG for better strength and durability (PETG has NOT been tested with this print)