CCFA, Crohns and Colitis Foundations of America has walks all over the United States and their research helps to fund research that helps us all. Google them, they also have summer camps for children and/or teenagers with IBD and I know many j-pouchers that volunteer as counselors at those camps.
I have not heard of a specific Pouchitis walk. I guess Dr. Shen's office at the Cleveland Clinic might be a place to inquire about it.