Hi cmadparty,
The better options or possibilities I’m aware of in and around the Boston area (subject to making sure that any mattress you are considering meets the quality/value guidelines here) are listed in post #2 here.
I don’t know which of the local options on the Boston list carry latex toppers (you would need to check their websites or call them)
There is more information about choosing a topper in post #2 here and the topper guidelines it links to which along with a conversation with a reliable and knowledgeable supplier (that can provide you with good information about how their toppers compare to each other or to other toppers they are familiar with that are available on the market) can help you use your sleeping experience as a reference point and guideline to help you choose the type, thickness, and firmness for a topper that has the least possible risk and the best chance for success. It also includes a link to a list of some of the better online sources for toppers I’m aware of and a link to the online suppliers that have good exchange/return policies as well (just in case the topper you choose doesn’t turn out as well as you hoped for).
There is also more about the different types and blends of latex in post #6 here but in general terms any type or blend of latex would be a very durable material.
All the latex you are likely to encounter (either Dunlop or Talalay that is made with either natural or synthetic rubber or a blend of both) will have a reliable certification such as Oeko-Tex, Eco-Institut, or Greenguard Gold (see post #2 here) and based on actual testing I would consider any type or blend of latex to be a very “safe” material in terms of harmful substances and VOC’s.
While I can certainly help with “how” to choose … I don’t make specific suggestions or recommendations for either a mattress, manufacturers/retailers, or combinations of materials or components because the first “rule” of mattress shopping is to always remember that you are the only one that can feel what you feel on a mattress and there are too many unknowns, variables, and personal preferences involved that are unique to each person to use a formula or for anyone to be able to predict or make a specific suggestion or recommendation about which mattress or combination of materials and components or which type of mattress would be the best “match” for you in terms of “comfort” or PPP (Posture and alignment, Pressure relief, and your Personal preferences) or how a mattress will “feel” to you or compare to another mattress based on specs (either yours or a mattress), sleeping positions, health conditions, or “theory at a distance” that can possibly be more accurate than your own careful testing (hopefully using the testing guidelines in step 4 of the tutorial) or your own personal sleeping experience (see mattress firmness/comfort levels in post #2 here).
I also don’t keep a record of the individual mattresses or their specs that the retailers and manufacturers in the hundreds of forum lists throughout the forum carry on their floor or have available online (it would be a bigger job than anyone could keep up with in a constantly changing market) but checking their websites and making some preliminary phone calls to the retailers/manufacturers that are on the local lists is always a good idea before you decide on which retailers or manufacturers you wish to deal with anyway. This will tell you which of them carry mattresses that would meet your specific criteria, are transparent about the materials in their mattresses, and that carry the type of mattresses that you are interested in that are also in the budget range you are comfortable with. Once you have checked their websites and/or talked with the ones that interest you then you will be in a much better position to decide on the ones that you are most interested in considering or visiting based on the results of your preliminary research and conversations.
There are certainly many people who tend to prefer innerspring/latex hybrids and there is also more about innerspring support cores vs latex support cores in post #28 here and in post #2 here and some innerspring/latex hybrid sources that may be worth considering in post #2 here.
Phoenix