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. Go down and check coupons out. Remember to check price history if it is available. Let’s see what best price is ATM.
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. You can get coupon down below.
Link: Banggood product page
1. ($11.67): BGRCParts8
paste coupon code in your cart and click Apply after clicking “Proceed to checkout”. Click to copy code and open shop.
Additional Banggood coupons: first page and second page
Old coupons (from the oldest to the newest): Parts8, 2020CNY, BGVDay10%off, bGhOnEy10, BGTT10, BGSS10%SW, BGRCRR9, BGRC902, BG11SHOP, BGDAVIS, 13f142, BGradio9, BG70e5fc
(there’s a little possibility that old coupon will work)
Price history and price alert
Check out price history chart (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)).