Aliexpress
Here are coupons that you can use.
Latest coupon and price update (UTC):
Banggood
Banggood warehouse is located in China. You can get coupon down below.
Link: Banggood product page
Coupon (21.88 USD): BG00c906
(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): BGZPBC15, BGTY704CP, BGCuponation10, BGHONEY2110, BG10OFFAFF, BGwhielabel, 13f142, BGdea251, BG10OFFAFF1, BGb8c933, BG4d9120, BGAlerabatod, BGAlerabatdo, 00c906, BGe46870, BG7280ff, Tabby20, 8Couponsde, BG36e006, MVC8SPRING, 8BGwbg2204, 2203ActiesNL, tRaDetRaCKeR, BG2bb7a1, BG5d2ea4, BG8ReviTrage, Cuponation9, BG073996, BGc363fd
(you can check these old coupons out, but these probably won’t work)
Price history and price alert
Price history (for all/most countries) for Fun Home 500ml Insulated Vacuum Cup is here.
Price records source(s): Banggood
Click on image to enlarge. 
You can set price alert (for Banggood).