Updated on Jan 24 2023 to include a mount for the front of the rear seat storage area on the Rivian R1T.
This is the holder for the JR Products Cupholder which is available off of Amazon. There are two versions that are uploaded - one that mounts on the front doors (not rear) and another that mounts on the passenger side of the storage area rail in front of the center console.
You'll need to print two of either to install the cupholder. You'll also need the following items:
Print in PETG or ABS.
This product is available for purchase here: https://riviparts.com/products/aux-cup-holders
Discuss this product at https://www.rivianforums.com/forum/threads/work-in-progress-auxiliary-cup-holders-removable-collapsible-adjustable.7570/page-2#post-205962
The author marked this model as their own original creation.