Aliexpress
Click here… to search for JDRC JD-20S Drone 2MP 3 Batteries on Aliexpress
Here are coupons that you can use.
Latest coupon code price check (UTC time):
Banggood
Banggood warehouse is located in China.
Link: Banggood product page
Coupon (86.48 USD): BANGGOODSD
Coupon (87.41 USD): Drones6
(CouponsFromChina.com tip: apply code in your basket (cart) after clicking “Proceed to checkout”. Click to copy code and open shop)
Old coupons (from the oldest to the newest): ed39c6, rchobbies8, AFfbG10, bGhOnEy10, Email5, BGDAVIS
(these coupons are old, so probably won’t work)
Price history and price alert
Here is price history (for all/most countries) for JDRC JD-20S Drone 2MP 3 Batteries.
Price records source(s): Banggood
Click on image to enlarge. 
You can set price alert (for Banggood).