Hi jethrodesign,
The component post here includes the better sources for latex toppers I’m aware of but there are 1" Talalay toppers available from …
I don’t have any specific “spec” suggestions no and most of them would be structurally capable of supporting a latex mattress and would have a suitable support surface with small enough gaps between the slats. You can also see some comments about the pros and cons of flexible foundations (either with or without the ability to change the tension/firmness in certain areas) in post #2 here and the foundation post here has a number of links to various flexible foundations.
Phoenix