The fork would need to be suspension corrected for a 26" wheel and an 80 mm travel fork. It's probably about 450 mm axle to crown, give or take. Thus, you could probably use a current Surly Ogre non-suspension corrected fork, because it's designed for 29" wheels and tires and has an axle to crown measurement of 447 mm.
The Ogre fork would be great for a touring conversion, as it has bosses for up to 4 cages, or 2 cages and mid-blade mounted front rack, giving you a lot of options.