it is ridiculous to search for it in Belgium or Europe, America is the richest place in plants. Me living in Greece i can only get plants from Europe, that is mostly Italy and Holland. Don't worry, only persevere, tamarillos are easy plants to grow. I know sibundoyensis is not currently available at tradewindsfruit, but just keep watching that site, it is a reliable site, they only sell live and viable seeds, i buy from them since years and i can give my word for them. Of course, there are nurseries too selling living plants in America, countless times i have found plants sold on line by American nurseries but i was disappointed because normally they do not send plants overseas. For me you sound like the Chinese proverb "holding a lantern and searching for fire". Persevere for three years to have tamarillos in your place, it will reward you, betacea's flowers are so lovely scented! By the way, have you seen huertasurbanas in this forum? Based in Argentina, he sells many good seeds, i recommend his annonaceae.