Basically copy coupon, view price history or create e-mail price alert. What is best price?
Aliexpress
There’re some similar (or not) items on Aliexpress
Click here to search by yourself. Here are coupons that you can use.
Latest price update (UTC time):
Flash-ready indicator: Red indicator lights, Dimensions: 83x154x112mm/3.3×6.1×4.4in, Color temperature: 5600+200K, Auto-zoom (flash coverage set automatically to match the lens focal length and image size), Model: TT685-N/C/S/F/O, Net Weight: 395g/13.9oz., Stroboscopic flash: Provided (1-99Hz), Optic slave triggering: Provided (S1 & S2), Compatible cameras: for Canon/Nikon/Sony/Fuji/Olympus DSLR cameras (TTL autoflash), Flash duration 1.2ms or shorter, Size: 83(W)x154(H)x112(D) mm = 3.3×6.1×4.4 in, , Brand: Godox, Internal power: 4 AA batteries, Guide No. 58/190 (at 105mm focal length / ISO 100 in meters/feet), High-speed sync: Provided (Up to 1/8000s / first-curtain sync / and second-curtain sync), FV lock: With button, Power saving: Power off after a certain period (approx. 1.5min.) of idle operation, Effective range: 0.7-6m/2.3-20feet, Manual zoom: Swinging/tilting flash head / 270 degrees horizontally and 90 degrees vertically (bounces flash), Battery life: 100-700 flashes, Flash coverage 24-105mm (14mm with wide panel), Recycling time: Normal flash: approx. 0.1-5sec, Exposure control system: TTL autoflash / manual flash
Banggood
Banggood warehouse is located in China. I’m afraid that there’s no working coupon in Banggood.
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!
Exclusive Allowance Coupons: https://bit.ly/3xWgD9k and https://couponsfromchina.com/short/5cd
Old coupons (from the oldest to the newest): Couponsde7, 2022ACTIESNL, 2203ActiesNL, BG1efeb0, MVC8SPRING, 8BGwbg2204, tRaDetRaCKeR
(there’s a little possibility that old coupon will work)
Price history and price alert
Here is price history (for all/most countries) for Godox TT685 TTL HSS Camera Flash Speedlite.
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)).