Aliexpress
Click here… to search for Likebook Mars T80D 7.8 inch Ebook Reader on Aliexpress
Here are coupons that you can use.
Latest price update (UTC time):
Banggood
Banggood warehouse is located in China.
Link: Banggood product page
Coupon (223.19 USD): elec
Coupon (223.19 USD): AFfbG10
(CouponsFromChina.com tip: paste coupon code in your cart and click Apply 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): ee9063
(sometimes old coupons work, so you can check them out (this site checks them on every price update))
Price history and price alert
Price history (for all/most countries) for Likebook Mars T80D 7.8 inch Ebook Reader is here.
Price records source(s): Gearbest, Banggood
Click on image to enlarge. 
You can set price alert (for Banggood).