In the USA, Canada balsam is available from Carolina Biological and a couple other vendors, but I'm not sure if they ship internationally. You can Google their full catalog, however, and get the information there. I now use gum Damar, another natural resin that will not deteriorate with time, for my histological work. It is as permanent as Canada balsam, but with lower acidity and therefore less impact on the stains. Have you tried it?