Aliexpress
Click here… to search for Memory Foam Seat Cushion Pad [EU] on Aliexpress
Here are coupons that you can use.
Latest coupon code price check (UTC time):
Banggood
Banggood warehouse is located in Europe 
. I don’t know if this is a good price – number of records in my database is too low! One coupon is available. Cool!
Link: Banggood product page
Coupon (33.83 USD): BG589b2e
(CouponsFromChina.com tip: just apply this code 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): BG56cb25, BG6cb22c, BGb1be3b, Cuponation9, 9OFFSUMMER, BG8ReviTrage, BGGutscheine, BG00c906, BG8OFFCOUPON, TTBLACK5
(you can check these old coupons out, but these probably won’t work)
Price history and price alert
There is only one database record (it was for 17.99 USD), so you can’t see price history chart.
You can set price alert (for Banggood).