I love topknots on Yorkies, and it doesn't matter if they are a boy or a girl, after all, in the show ring all Yorkies are required to wear a bow.  Men wear bow ties, why can't male yorkies wear bows?  With skin-kids you have to worry about warping their identities, not so with fur-kids, other dogs won't tease him if he's wearing a bow!  Start with just a band, and let him get use to that, and gradually he'll get use to wearing bows, but you put the bow over the band, don't use the bow to make the topknot.  By the way, some of us call them ninja knots, instead of topknots! 
