Hi 1sweetdream,
The better options and possibilities I’m aware of in the Cedar Falls area are listed in post #4 here but you have already found two of the better options that are reasonably local to you.
They would be the best source of information about all the materials and the type and blend of latex that they use inside their mattresses (any information I would be able to find out would come from them). They don’t show a “Latex Pure” mattress on their site but based on their website they appear to use Talalay latex in their mattresses (which is a high quality material). They don’t say whether it’s blended or 100% natural (although blended would be more likely) so you would need to ask them.
Phoenix