Right now the best price with coupon code for Eachine StingPad 5.8G 16dBi Flat Panel FPV Antenna is $8.99 (in Banggood). You can create price alert here, copy coupons and view price history. Let’s see what best price is ATM.
Item Name: StingPad Antenna, Connector: SMA, Gain: 16dBi, Impedance: 50 ohms, Radiation: directional, VSWR: < 1.3: 1 (5722 - 5945MHz), Beam width 42 degrees (H + V), Brand Name: Eachine
Latest coupon code price check (UTC time):
Banggood ($8.99)
Banggood warehouse is located in China. Hmmm… There is no active coupon in Banggood at this moment. Low/high price? Pretty good price – average ($10.06) is higher than current one!
Link: Banggood product page
Price: $8.99
Exclusive Allowance Coupons: https://bit.ly/3xWgD9k and https://couponsfromchina.com/short/5cd
There were country-specific coupon codes published on Couponsfromchina social channels and price alerts. Coupon price may vary by country, because there’re different VAT rates, shipping cost etc. There is a chance that some latest coupons are still working:
Old coupons (from the oldest to the newest): BGEachine10, BGRCEachine, Tabby20, BGRCT10, BGToys8, BGMatt2022, BG25d4e7, BG589b2e
(probably won’t work, but you can try them out)
Aliexpress
There’re some similar (or not) items on Aliexpress
Click here to search by yourself. Here are coupons that you can use.
Price history and price alert
Price history (for all/most countries) for Eachine StingPad 5.8G 16dBi Flat Panel FPV Antenna is here.
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)).