T-Type 900MHz RC Receiver Antenna FrSky R9 Mini MM (Banggood, Aliexpress: Connector: IPEX 4, RF Cable: RG1.13, Cable Length: 85 mm, S.W.R.: <= 1.7, Compatibility: FrSky R9 Mini/ R9 MM Receiver, Frequency: 868/915 MHz, Antenna Gain: 2.0DBi, Width: 168 mm, Weight: 1.3 g, Working Temp: -40~80℃, Impedance: 50 Ω, Polarization: Horizontal polarization, Humidity: 95%~100% RH (the best price with coupon)).
Basically copy coupon, view price history or create e-mail price alert. What is the 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 price update (UTC time):
Banggood
Banggood warehouse is located in China. I found coupon for you. Check this out.
Link: Banggood product page
1. ($11.67): BGRCParts8
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): Parts8, 2020CNY, BGVDay10%off, bGhOnEy10, BGTT10, BGSS10%SW, BGRCRR9, BGRC902, BG11SHOP, BGDAVIS, 13f142, BGradio9, BG70e5fc
(these coupons are old, so probably won’t work)
Price history and price alert
Here is price history (for all/most countries) for T-Type 900MHz RC Receiver Antenna FrSky R9 Mini MM. The lowest price was: $3.39.
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)).