Pretty much any other 4Runner rear springs you find are going to be just as saggy as yours.
Option 1, OME spring pack. Should match the ball joint spacers perfectly. This would be my recommendation, assuming that's all the lift you'll ever want, see below.
Option 2, get a 3" lift spring from about anywhere, and crank your torsion bars to match. Blech.
Option 3, rebuild your existing spring pack. Two leaves inserted should bring you back to stock without being too stiff, then maybe a 5.5 or 6 inch shackle to match the ball joint spacer lift. I've done this, it rode ok. I like the OME springs better.
Option 4, add a leaf and leave the blocks. I would recommend against this, for lots of reasons.
Option 5, Chevy or Ford spring swap. Takes fab, and you'll have to mess with building the pack to get the height right, but once you've got it right the longer springs ride really well.
Option 6, ZUK mod. Google it. I've done it before, it works, it's not ideal.
After that it gets expensive. Companies like Alcan or Deaver will build you a custom spring pack to your exact specifications, or there's a couple of different link conversion kits on the market. My suggestion would be to figure out now exactly what height you want it, find the best way to go straight to that height, and leave it there. If you think you might want to go higher than the 2 inches you're working towards now, then do that and save yourself the intermediate step.