Hi katafus,
The mattress shopping tutorial includes this link to a list of the members here that sell mattresses online and while all natural latex mattresses tend to be a more costly choice than mattresses that use lower cost materials … several of them sell queen size 100% natural latex mattresses that are well inside your budget range but of course this will also depend on the thickness and design of the mattress and/or on the type of latex you prefer as well.
There is also more about the different types and blends of latex in post #6 here and it may also be worth considering versions of latex that aren’t 100% natural which are also very high quality and safe materials and may be less costly.
The better options or possibilities I’m aware of in the northern VA area (subject to the guidelines here) are listed in post #2 here.
Phoenix