Hi Nibrin,
welcome to the forum. It's actually quite difficult to find cones and stuff in Belgium. As for Brussels I think your best shot is twin shop
http://www.twin.be/ . Another possibility is to post your question on
www.rouliroula.com, the most important inline forum of the french speaking belgians and read by lots of people from brussels.
You're always welcome in Hasselt to come skate with us and test those new wheels

greetz.
Tim