Aliexpress
Click here… to search for MACWHEEL D2 Self-Balancing Electric Unicycle on Aliexpress
Here are coupons that you can use.
Latest price update (UTC time):
Banggood
Banggood warehouse is located in China. I found coupon for you. Check this out.
Link: Banggood product page
Coupon (817.19 USD): ERidingMarch
(CouponsFromChina.com tip: apply it 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): e1cbe5, e2bcea, BgAuMotor, TTxBG10, 502C6B, BGMOTO25, BGAutos, 7bcdf9, BGAFF7OFF, BGEBSC15
(probably won’t work, but you can try them out)
Price history and price alert
Price history (for all/most countries) for MACWHEEL D2 Self-Balancing Electric Unicycle is here.
Price records source(s): Banggood
Click on image to enlarge. 
You can set price alert (for Banggood).