Reusable Bag is the 1st item unlocked in the Eco Shop. The Eco Shop is a Regional Commercial building that is unlocked at Level 25 and requires the Green Valley region to be unlocked.
A Reusable Bag can be produced in 22 minutes in 2 stages without using the Global Trade HQ or a Speed-Up Token. Based on this production time, the simoleons/minute is 5.45. (High-tech Factories and 3-star shops were used for these calculations.)
Reusable Bags were originally called Cotton Bags as you can see on EA's official website about regions. However the name was later changed to Reusable Bag.