Aliexpress
Here are coupons that you can use.
Latest price update (UTC time):
Banggood
Banggood warehouse is located in China. There is one coupon right now! Check this out.
Link: Banggood product page
Coupon (9.65 USD): BGRCParts8
(CouponsFromChina.com tip: you should apply the coupon in your cart after clicking “Proceed to checkout”. Click to copy code and open shop)
Exclusive Allowance Coupons: https://bit.ly/3xWgD9k
Old coupons (from the oldest to the newest): BR0703C, 502C6B, 10OFFBrand, TTxBG10, AFfbG10, BGVDay10%off, BGMPB2020, BGAFF10OFF, bGhOnEy10, BGdragonBoat, BGSS10%SW, BGRC902, BgoFErTaSchInA10, BgcLuBofErtA10, Parts8, BGDAVIS, BGHONEY2110
(these coupons are old, so probably won’t work)
Price history and price alert
Here is price history (for all/most countries) for Racerstar BR0703C 0703 1S Red RC Motor.
Price records source(s): Banggood
Click on image to enlarge. 
You can set price alert (for Banggood).