What cantilever brakes are compatible with Surly Pugsley 100mm front fork?
Any medium-profile or low-profile cantilever brakes should work on the Pugsley; so long as you're using the Large Marge rims the effective cantilever post to rim spacing should be basically the same as a normal bike. The default spacing for most cantilever bosses is 80mm for use with a ~25mm wide rim.  On the Pugsley the bosses are spaced 120mm for a 65mm rim.

The Shimano "link wire" style straddle cables will almost certainly be too short,   For clearance, with whatever brake you use I'd plan on making it work with a high-quality yoke and a long straddle cable, as used on a wide-profile cantilever. You might even be most successful dialing in your own using a set of cable knarps.