Hi HairCandyKina,
Post #2 here has more information and guidelines about buying a mattress for a child and includes a number of links to the better forum posts and topics about mattresses and children that include some of the better options I’m aware of as well. It also includes a link to more information about “safe” materials…
As you probably know … your budget is very low and you won’t find the best quality materials in this budget range so once you have decided on the type of materials you are comfortable with having in your mattresses then your goal is to find a mattress that is both “safe enough” and is the best quality/value that is available in your budget range.
Outside of the mostly online options that are linked in the previous children’s topic … some of the better options or possibilities I’m aware of in the Mobile, AL area (subject to the quality/guidelines here) are listed in post #365 here.
I’m not familiar with Lee Street Mattress and they have only been in business for about 4 years but based on the information on their site and on their facebook page they would seem to fit the profile of the type of factory direct manufacturer that would be well worth including in your research.
I’ve added them to the Mobile/Pensacola list as well … and thanks for letting me know about them 
Phoenix