Ch3 Throttle, Ch2 Elevator, Size: Receiver 47mm*27mm*12mm / GPS 29mm*28mm*8mm, Application Protocol: Compatible with D8R open source protocol, Ch1 Aileron, Ch4 Rudder, Communication distance: >800 meters, Application Technology: 2.4G full frequency ACCST frequency hopping technology, Application frequency: 2.40GHz – 2.48GHz, Weight: Receiver 9.8g / GPS 9g, Power Source: 3.3V – 7.4V.
Basically copy coupon, view price history or create e-mail price alert. Do you want to know what the best price is?
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. I don’t think there is an active coupon right now – at least in my database.
Link: Banggood product page
Price: $-3
It looks like this item is out of stock in Banggood. If you found it then please send me the link. I will replace it.
Click here to search on Banggood!
Additional Banggood coupons: first page and second page
Old coupons (from the oldest to the newest): BgcLuBofErtA10, BGAFF10OFF, BGCuponation10, BGDAVIS, BGHONEY2110, BGPlane-5, Parts8, BGAir5
(these codes were not working in latest coupon update, but you can check them out anyway)
Price history and price alert
Here is price history (for all/most countries) for Hobby Porter FR810 8CH RC Flight Controller with GPS. The lowest price was: $36.61.
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)).