Though it wasn’t called a “Top Bag” when it was first offered, I believe that the Stephenson Warmlite bag was the first bag on the market to dispense with the insulation in the bottom of the bag because the premise was that the pad would provide the warmth as well as the cushion. I bought mine in 1987. It had been on the market for over 20 years then.
One of the feature stories on the Home page states that MacPac from New Zealand was the first.
Another exception I can think of (though, again, it’s not called a “Top Bag”) is the Feathered Friends Great Auk. I bought one of those in 1993.
