Ecological Shoes are the 2nd 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.
An Ecological Shoe can be produced in 264 minutes in 3 stages without using the Global Trade HQ or a Speed-Up Token. Based on this production time, the simoleons/minute is 2.84. (High-tech Factories and 3-star shops were used for these calculations.)