Most research firms get raw data and then derive whatever information they need from the data (e.g. statistical analysis, demographics). Thus, in the end, you may need to do such yourself (get the raw data) and then derive whatever demographic information you need from that data. Thus, Stocks & Commodities don't have published demographic study but they do have the "raw data" that would allow you access to thousands of traders via the mailing list so that you can contact those traders to derive whatever demographic study (data) you're looking for. That's exactly what many research firms do. Just something to think about because it seems like you're looking for the information already prepared for you. Analogy, you may have to go to the grocery store and buy all the ingredients you need to make your meal if nobody has the meal already prepared for you.
You are absolutely correct that my preference is for a current demographic study conducted by professional demographers. I've made that abundantly clear in this thread. The reason for that is that I prefer to have the most accurate information possible, and a demographer who is an expert in his/her field is certainly going to do a better job than me. I'm great with numbers and basic statistics, but a true demographer is going to produce a more complete and accurate study than me. If I can't find what I'm looking for, then I'll either pay to have one done, or do one on my own. I'm not adverse to putting in the effort to do it myself, I'm just looking for most accurate statistics I can possibly obtain.
The other option I'm already pursuing, is working with a university PhD candidate to produce such a study.