Just check coupons out (with price alert and history). Best price?
Size: 210*110*295, Power Consumption: 28W, Flow Rate: 1-2L/min, Oxygen Concentration: 50%-80%, Net Weight: about 1.98KG, Negative Ions: about 300 /000 pcs/cm³ (electron emission), Working Pressure Range: ≥83kPa, Oxygen Producing Method: VPSA method /, Measurement Environment: 20 ℃ / normal pressure / humidity 60%RH, Noise: about 45dB (measured at 1 meter away from the machine), Power Supply: AC100V-240V /50Hz/60Hz, Inhalation Method: nasal suction type and inhaler, Spray Speed: ≥0.2mL/min, Working Air Flow: ≥6.7LPM
Aliexpress
There’re some similar (or not) items on Aliexpress
Click here to search by yourself. Here are coupons that you can use.
Latest coupon and price update (UTC):
Banggood
Banggood warehouse is located in China.
Link: Banggood product page
1. ($242.27): BG1efeb0
2. ($244.91): Terence
3. ($244.91): 2203ActiesNL
4. ($247.54): BG00c906
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 and https://couponsfromchina.com/short/5cd
Old coupons (from the oldest to the newest): BGJP20669, BGOxy10, BGJP2066, BGJP20661, BGd0b05d, 00c906, ADMITAD2212, 2022ACTIESNL, Tabby20
(system checks these coupons on every price check (like once per 24 hours), but you can check them out anyway)
Price history and price alert
Do you need price history chart (for all/most countries) for 1-2L Portable Oxygen Concentrator Generator? There we go.
Price records source(s): Banggood
Click on image to enlarge. 
You can set price alert (for Banggood and Aliexpress (only if product name will be the same as on Banggood and I will post it on social media though, so it’s more like Banggood price alert)).