Colors: Standard Colors, Plug: XT30 Plug, Battery Parameter: URUAV 11.4V 300mAh 40C/80C, Capacity: 300mAh, Weight: 27g, Continuous Discharge Rate: 40C/80C, Size: 65X18X11mm.
Basically copy coupon, view price history or create e-mail price alert. What is best price?
Aliexpress
There’re some similar (or not) items on Aliexpress
You can use link bot to get even lower price:
Click here to search by yourself. Here are coupons that you can use.
Latest coupon and price update (UTC):
Banggood
Banggood warehouse is located in China.
Link: Banggood product page
1. ($31.49): bGhOnEy10
2. ($31.49): BgoFErTaSchInA10
3. ($31.49): BgcLuBofErtA10
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 and https://couponsfromchina.com/short/i1u
Old coupons (from the oldest to the newest): BG4pcsUR, AFfbG10, 502C6B, BGVDay10%off, BGRC902
(I don’t think these’re gonna work, but you can try ’em out anyway)
Price history and price alert
Check out price history chart (for all/most countries) for 4Pcs URUAV 11.4V 300mAh 40C/80C 3S RC 4.35V Battery. The lowest price was: $27.99.
Price records source(s): Banggood
Click on image to enlarge. 
You can set price alert (for Banggood and Aliexpress (only if product name will be the same as on Banggood and I will post it on social media though, so it’s more like Banggood price alert)).