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Fireplace Accessories
I think your best bet would be to check out antique and used furniture shops.
I found a fireplace grate at Stefantiek near the Sablon - http://bestofbrusselsblog.com/2011/11/09/stefantiek/
and recently bought some an acessories set for EUR 30 at Troc - http://bestofbrusselsblog.com/2011/10/17/troc-this/