Never actually seen it for sale. I got a juicer and started juicing my own. If you really wanna help that liver, get into it and also throw in some carrot and Apple as well. Its commonly referred to as 'Apple Beetroot Carrot, or ABC". Definately get on the beetroot and try the other extras as well.
One other thing you can do pretty much immediately is to go see a Chinese Herbalist. Tell him what your doing and your liver is stressed etc. He should give you some herbs to boil and drink to strengthen and help repair your liver. There are also some Chinese Herbal Pills (all legal ) that are like a specific liver tonic. They were originally made for women on their period as their liver seems to get stressed around that time as well. I have used both the pills and the herbs in the past, with great success and highly recommend them both. I used the pills constantly for 6 months and WOW, they were great, really got my liver back to speed.