I took a basic window-mounted hanging cup holder with a flexible plastic insert (for the space between the window and the door), folded the insert and wedged it between the carpet and the plastic covering for the driver's seat belt retractor. The result is that the cup holder is held by the plastic and the carpet and it hangs in the space between the side rail, the bulkhead and the left rear corner of the driver's seat. Perfect solution.
Low cost, low weight, no drilling, no mess, easily removable, but stable.
Low cost, low weight, no drilling, no mess, easily removable, but stable.