ECE 4/6, now I need helper bags

[Jack_71C10]

I heard alot of people on here say they added helper air bags to their 4/6
dropped truck, but noone says what kind they use. I need them for the rear
of my 71 c/10, but can't even find any for stock height. I want the kind
that goes inside the coil spring if there is something out there that works.