so far I've read that Barleans with lignans is the best in terms of quality in the US, and it's organic/cold pressed, unfiltered.
I am not sure if you can find it in your country, but you may want to call them and ask if they would ship overseas: www.barleans.com
If you call Barleans directly and tell them that your son has cancer, they will give a special price for cancer patients. It's almost half price you pay in the store.