Aliexpress
Click here… to search for Fatshark Dominator HD3 RC FPV Goggles on Aliexpress
Here are coupons that you can use.
Latest coupon code price check (UTC time):
Banggood
Banggood warehouse is located in Hong Kong. There is one coupon available! Pretty cool, huh?
Link: Banggood product page
Coupon (359.10 USD): f62884
(CouponsFromChina.com tip: coupon code has to be applied in shop’s cart after clicking “Proceed to checkout”. Click to copy code and open shop)
Old coupons (from the oldest to the newest): 14c24d, e2bcea, BF339, 502C6B, 6d27ab, 04f3d2, 387484, 209200
(these coupons are old, so probably won’t work)
Price history and price alert
Price history (for all/most countries) for Fatshark Dominator HD3 RC FPV Goggles is here.
Price records source(s): Gearbest, Banggood
Click on image to enlarge. 
You can set price alert (for Banggood).