For the most part it is only smaller 321A schools that do not have leagues to wrestle in. For the most part all of the 6A, 5A, and 4A programs have wrestling and they are also in leagues with similar sized schools making it easier to have a league tournament or dual schedule. Of the smaller schools it seems like many are on the eastern half of Kansas. Here is a list of the ones I can think of off the top of my head:
Erie
Central Heights
Mission Valley
Sedgwick
Flint Hills
Remington
Chase County