Aliexpress
Click here… to search for Graupner GM X-8N RC Transmitter on Aliexpress
Here are coupons that you can use.
Latest coupon and price update (UTC):
Banggood
Banggood warehouse is located in China. I found coupon for you. Check this out.
Link: Banggood product page
Coupon (227.46 USD): Parts8
(CouponsFromChina.com tip: just apply this code in your cart after clicking “Proceed to checkout”. Click to copy code and open shop)
Exclusive Allowance Coupons: https://bit.ly/3xWgD9k
Old coupons (from the oldest to the newest): BGGMX8N, BG10PARTS, BGAFF10OFF, BGTT10, bGhOnEy10, BGdragonBoat, BGSS10%SW, bgshOOp10, BGRC902, BgoFErTaSchInA10, BgcLuBofErtA10, BGCuponation10, BGDAVIS, BGHONEY2110
(sometimes old coupons work, so you can check them out (this site checks them on every price update))
Price history and price alert
Do you need price history chart (for all/most countries) for Graupner GM X-8N RC Transmitter? There we go.
Price records source(s): Banggood
Click on image to enlarge. 
You can set price alert (for Banggood).