Pens that write on polymer clay...

....and don't smudge! do any exist? The only ones I have found to work so far are the Eberhard Faber Decoro Lackmarker.  Sometimes I need a pen when I am doing a certain design on my cake toppers and also for when I write the couples names on the base of the topper but finding one that works is hard!  If anybody out there can point me in the right direction of preferably a fine black pen but a pack of colours would be good too, I would be most grateful! :)