On my 2nd gen I couldn't find any that would fit with the 4" lift.

So are there any that will work on my 3rd gen with a 3" revtek spacer lift?

I just want to lessen the rear end sag when towing. Are there any other options, like air shocks?

 

Summit racing has the Air Lift bags for 3rd gen 4runners. You can buy just the bags , and inflate them using sop air or you can get the full kit that comes with an onboard compressor to do it on the fly. I was looking at doing this to be able to tow my buggy with our 02 4r but I ended up with a 3/4 ton truck for that duty!
hope this helps,
Richard S.

website for them is ww.summitracing.com