There aren't any Pepakura models for the Reach Trooper part of the Reach ODST armor except for the helmet, which why I made mine from scratch (click my sig below) using foam rubber mats. Another member here Sgt. Forge, is making his from scratch as well but he was able to design his Reach Trooper armor in Photoshop I think, and he is sharing them HERE. Good luck and I hope this helps!
There are some small differences but they are rather minor. Hugh's helmet has files that can be added to it to make it the different configurations including the Reach version.
Check out Kirru's (I think I misspelled his name) HD Reach files and he has references pictures for Reach ODSTs and some of the files (not the trooper core).
Indeed they have differences, but I doubt there is a file more accurate to Reach's helmet than the one of Halo 3: ODST. I wish Reach had it's own file, though :\