Hi mg517,
That’s great news and thanks for the update 
The topper and component list in post #4 here had several sources for 1" memory foam toppers in a link to post #1 here which had the results of some earlier searching I did for 1" memory foam toppers but it seems that most of them have been discontinued (although as DahliaM mentioned Foamorder still carries them).
With a thin topper the density of the memory foam is not as important because they are so easy to replace and it’s more common to find them in a 3 lb or lower density than 4 lbs and up but I would still tend towards 4 lbs and up because this will have more of the “memory foam effect” and won’t be as flimsy. You will sink into (or “through”) lower density memory foam more easily.
The thickness of a topper that works best depends on what it is going on but the more “subjective” guidelines I usually suggest are …
1" = Just a touch to a little
2" = A little to a fair bit
3" = A fair bit to a lot
This can help you use your actual experience on the mattress as a reference point. 2" is a good “average” choice.
I spent some time looking and didn’t find any other sources for 1" memory foam toppers in 4 lbs or more although there are a few that are in the 3 lb or less range that a google search brought up.
Phoenix