RF power: +22DBM, Operating frequency: 2.4G ISM band, Software Compatibility: Suitable for radios using OpenTX or er9x/ersky9x, Item name: JP4IN1 transmitter module, Working current: <=100ma, Module bay compatibility: FRSky, Jr and other dimensions: 64*49*33 (without antenna), Working voltage: 6-9v, 20K RAM), Net Weight: 42g (including antenna), Main control chip: STM32F103CBT6 (128K ROM. Check coupons or create price alert down below. 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 coupon code price check (UTC time):
Banggood
Banggood warehouse is located in China. There is one coupon available! Pretty cool, huh?
Link: Banggood product page
1. ($57.37): Parts8
you should apply the coupon in your 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): BGaDmITAd, BGCITYADS2019, BGMD10, BGJPN30, 2020CNY, BGVDay10%off, bGhOnEy10, bgshOOp10, BGRC902, BGRCRR9, 7d18f7, BGCuponation10, BGDAVIS
(there’s a little possibility that old coupon will work)
Price history and price alert
Price history (for all/most countries) for Jumper JP4IN1 RC Transmitter Module is here. The lowest price was: $30.99.
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)).