I run a Defender on my Pikes, though I don't think it's a great mudguard, flaps around too much and the brackets get worn introducing more play. I ended up using some zip ties to hold things more convincingly in place on the bracket, anyway...
Just unscrew the plug expander bit on the mudguard mount leaving you with the metal mounting bracket etc and use some washers and an appropriate bolt to screw the mounting hardwear directly into the hole in the steerer plug - job done.
I know a few people run the THE mudguard successfully as well on a similar principle.