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. Just check coupons out (with price alert and history). 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. There is one coupon available! Pretty cool, huh?
Link: Banggood product page
1. ($11.67): BGRCParts8
coupon code has to be applied in shop’s cart 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
(these codes were not working in latest coupon update, but you can check them out anyway)
Price history and price alert
Price history (for all/most countries) for T-Type 900MHz RC Receiver Antenna FrSky R9 Mini MM is here. 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)).