Hi paisley,
While I don’t know specifically how to define “melty”, it sounds like you’re looking for a more “old school” memory foam feel with slower recovery and a bit more of a “dense” feel. You may wish to look at some of the memory foam topper suppliers listed in post #4 here. Both Rocky Mountain Mattress and MattresTopper.com have “old school” 5 lb. memory foam without gel additives that you may like. Your best course of action would be a phone conversation with any business you’re considering and describe to them what you’re trying to match and they’ll be best able to advise you if they have anything available to closely match what you’re trying to find.
Phoenix