Just check coupons out (with price alert and history). Best price?
Frequency Range: 5.645Ghz to 5.945Ghz, Item Name: RC Antenna SWR Meter, Antenna Connector: SMA Female, Brand Name: OWLRC, 200mw, Screen: TFT 2.8″ Touch Screen, Power Input: DC 12V or 3S Li-Po only, Internal Signal Transmitter: 5.645Ghz to 5.945Ghz
Aliexpress
I could not find it on Aliexpress. Click here to search by yourself.
Here are coupons that you can use.
Latest price update (UTC time):
Banggood
Banggood warehouse is located in Europe 
. I don’t want to misguide you about the price. I don’t know if it’s good, because I don’t have enough records in my database… You can get coupon down below.
Link: Banggood product page
1. ($81.81): Cuponation9
coupon code has to be applied in shop’s 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/5cd
Old coupons (from the oldest to the newest): BGOwlRC15, BGPAYPALSS, BGBCFPV, Parts8, BGBCBG10, 502C6B, BGCITYADS2019, BGOWLRCSWR, 2020CNY, BGVDay10%off, BGTT10, bGhOnEy10, bgshOOp10, BGRC902, BGSWRMeter, BGFPV50-5, BGCuponation10, BGFPV-10, BGFPV10
(these coupons are old, so probably won’t work)
Price history and price alert
There is only one database record (it was for $81.81), so you can’t see price history chart.
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)).