An alternative to a traditional broadhead is a  
bow fishing tip .  I carry one when I go hiking because it can be used for fish as well as small game.  I like the penetrating point on it to augment the cutting blades I already carry.  It also has a hole drilled to tie a line.  It might be a little too single use for a small PSK, but I just wanted to mention it as an alternative.  
BTW, the link to Cabelas I gave was because it's the best picture I could find.  You can pick up just the tips at most large sporting goods stores and some archery and fishing shops for just a couple bucks.  
Chris.