Try Range product, Radium St Welshpool. Very good and worth a visit just for the smell. They sell essential oils, soap, shampoo and creme bases to make your own everything
Arnica You might find it needs a colder climate than Perth. Many people try to grow all sorts of herbs in unsuitable environments. Richters in Canada will have seeds See https://davesgarden.com/pf/go/1947/ for growing range You would be USA 8/9/10