Hi stuuke,
Post #2 here and the topics it links to has much more information about choosing a mattress for a child and includes a number of links to the better forum posts and topics about mattress and children that include many good options as well.
The better options or possibilities I’m aware of in and around the Kansas City area (subject to making sure that any mattress you are considering meets your criteria and the quality/value guidelines here) are listed in post #2 here.
Phoenix