Hi nap101,
Welcome to the Mattress Forum! 
Hopefully you’ve had a chance to read the mattress shopping tutorial which has all the basic information, steps, and guidelines that you will need to make the best possible choice … and know how and why to avoid the worst ones.
It’s unlikely that a latex/innerspring hybrid will have a 50/50 blend (at least by thickness) because the innerspring core will almost always be thicker than the latex comfort layers.
Post #2 here includes several manufacturers or retailers that sell innerspring/latex hybrids of various types and if you let me know your city or zip code I’d be happy to let you know about the better options or possibilities I’m aware of in your area as well. An innerspring mattress with latex comfort layers can make a great combination and a very durable mattress for those who prefer this combination of materials.
Phoenix