Hi @LiquidSnake The 20Ah is available on Amazon via 3rd party https://www.amazon.co.uk/Samsung-EB-P5300XJEGEU-20Ah-Battery-Pack
Alternatively the 10Ah is available with Mobile Fun (not bought much from them but have used in past without issue), they are awaiting stock on the higher capacity. https://www.mobilefun.co.uk/samsung/samsung-power-banks
I do not work for Samsung or make Samsung Products but provide independent advice and valuable contributions.
My Device- S21 Ultra 5G ( SM-998B/DS ) CSC= BTU , 12GB/256GB
One Ui 5.0,Android 13 .