Childrens Designer Clothes Shop...Where do I begin?

Ive been buying & selling on eBay for some time now (mainly personal belongings as a Private seller) & manage to make a small profit but Id like to try & expand into business selling, mainly childrens branded clothing & am looking into the possibility of opening a shop locally as I am aware of a demand in my area for such items but I have no idea of where to purchase stock. I have been unable to locate a wholesaler or supplier that stocks the labels Im looking for for children. Is it possible for me to contact the labels direct & request to purchase direct from them?