I put a 29er rigid fork in the soul for the first time the other week, lovely… It's this one:
http://www.carboncycles.cc/?s=0&t=0&c=43&p=197&
46.5mm axle-to-crown which isn't far off my 130mm revelations when sagged (they're 508mm at full length). I wanted to keep a fairly similiar feel since I'll be running both on the same bike (though not, I think, at the same time 😉 )
Not been able to really test it in normal conditions due to the snow but it's worked well so far. Glad I didn't go for a shorter fork, anyway- but to be fair, that's because I wanted the familiarity, not because I don't think the shorter ones would work well.
According to Exotic's website, the offset is the same for the 29er and 26er forks.
These are rotten pics, apologies, they're all I have and the bike has its revs back for now: