Total Chaos' Long Travel kit is available and in full production.
Other options if you really want more lift but won't be all that worth it:
Fabtech 6" lift using the subframe (will have to cut sections of the frame to make this fit though - just like any previous 6" lift). You'll have to tackle the rear on your own though - possible custom rear coils etc.
Simply the reason why no 6" kits on the 4runner. the rear axle that uses coils is the issue. If you had a Taco, it'll be super easy to get 6" in the rear usings AAL's or new leaves but since 4runners uses coils you're kinda screwed.
Remember, more lift = more headaches down the road.
Good luck