Aliexpress
Click here… to search for Digoo DG-MX10 Waterproof Wireless Speaker 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 (15.29 USD): BGBFAFF2019
Coupon (15.80 USD): PICODICOM
(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): 50DGMX, 0404digoo, 3ccc5a, BGDigoo15%, BG60MX10, BGAPPLIANCE, BGDGMX10, BGDG99, BGDGMX, BGDG9, BGDDG, BGUSDBS
(I don’t think these’re gonna work, but you can try ’em out anyway)
Price history and price alert
Here is price history (for all/most countries) for Digoo DG-MX10 Waterproof Wireless Speaker.
Price records source(s): Banggood
Click on image to enlarge. 
You can set price alert (for Banggood).