Wogster

Planning on adding fenders to my bike, the front fork is a suspension fork, so I need something like a P clamp in order to install the rods for the fenders. Here is the question, how do I determine the size of clamp that I need? Anyone know where I can find such a clamp in Canada

pmseattle

Usually in the electrical supply section of any large hardware store here in the US, dunno about Canada. Lots of bike shops have them here also since they have become ubiquitous as a workaround for attaching things to bike frames that lack the necessary braze-ons. You will also probably have to drill holes in the fender to attach it to your fork's brake arch with zip ties.
Just get the size that is nearest to the diameter of the fork leg. If it's slightly too big, wrap a piece of inner tube around the fork leg to make it tight. If it's slightly too small, fill the gap between the ends of the clamp with a stack of washers.

Wogster

Strangely enough, there is a hole in both brake arches, so the fender should attach there perfectly. There are mounts on the frame, just not the fork.