Aliexpress
Click here… to search for DEDAKJ DE-2A 2-9L Oxygen Concentrator [EU] on Aliexpress
Here are coupons that you can use.
Latest coupon and price update (UTC):
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!
Link: Banggood product page
Coupon (275.07 USD): BGSPRING8OFF
Coupon (275.07 USD): BGHONEYSP
(CouponsFromChina.com tip: you should apply the coupon 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): BGNEWYEAR8, BGacc0a1
(these coupons are old, so probably won’t work)
Price history and price alert
It doesn’t make sense to generate price history chart, because there is one price record which is: 274.99 USD.
You can set price alert (for Banggood).