Not quiet in line with what you're looking for, but you could get started tomorrow on this. I don't have a real use for a bunch of ruck gear outside of the exercise, and I don't need to spend the money on it right now.
I just use a 5.11 pack, 3L bladder, and some loaded Pmags, because no one had weights early last year when I started. You could throw in water bottles, 2 liters filled with water, whatever. That ends up with just shy of a 20 pound pack, which was plenty to get you started. Then I added a kid on my shoulders, so any where from 50 to 65 pounds.
I just started wearing my plate carrier though, which is a little over thirty pounds. So now I push anywhere from 60 to 75 pounds, at least four nights a week for at least three miles.
All that office chair dull back pain and neck stiffness, totally gone after starting that routine. Its been pretty good.