It's very difficult to buy Chinese Bitters in the UK.
You can make your own. You will need 100g Gentian Extract and 100g Bupleurum extract. That's about 100 ml of each. You'll take 5 ml (a teaspoon) made up of 2.5 ml of each. Follow the instructions on sensiblehealth.
I have seen both for sale by independent sellers on amazon.co.uk.