Hi amadden11,
Welcome to the Mattress Forum! 
I would first start with the expertise of the members listed in post #21 here who are all very experienced and knowledgeable and specialize in providing the type of help and guidance on the phone that can help you make good choices. There are a wide range of latex options included in the choices there and I believe that all of them compete well with the best in the industry in terms of their quality, value, service, and transparency.
There are also some lower budget latex and latex hybrid options that are listed in posts #3 and #4 here that are in “relatively” lower budget ranges (although some of these may be more than your budget).
For those that have an even more restricted budget then post #4 here and the posts it links to also include many of the better lower budget online options I’m aware of as well, but these generally will not be all-latex mattresses.
You may be able to save some money by building your own component latex mattress, and to that end you can look at the vendors in the component post here. However, creating your own DIY mattress does require a different set of skills and research and that may not be of interest to you as you mentioned in your post.
There are certifications for harmful substances and VOCs such as CertiPUR-US, Oeko-Tex and Eco-Institut that you can look for when looking at any mattress. There is more about these certifications and the posts it links to in post #2 here.
Phoenix