They will try to sell you caustic soda which is not what you want. I have done a quick search and others have sought this handy powder with no useful result. However good old Ebay will deliver at a price. I think in this day and age you will have a big problem taking on board diddlee airlines and the like but Les the van would bring it over for 5 euro or so. Otherwise have it posted over see below.

http://www.ebay.es/sch/i.html?_from=R40&_sacat=0&_nkw=Bartoline%20az%C3%BAcar&rt=nc&LH_PrefLoc=1&_trksid=p2045573.m1684


https://en.wikipedia.org/wiki/Sugar_soap

;)