I made a similar thread a while ago asking for this data, no one really responded.
Although this kind of data would be helpful from a marketing perspective most indie teams seem too fluid with constant churn and new orgs starting and dyeing all the time.
Even if we or anyone was willing to report this data publicly, it would be out of date in a month, and require a huge effort to track.
Best advise to OP is to contact GDC, and see if they be willing to share their data with you.
Data isn't free, and take time to collect. If you want the data for my org, you will need to go to my website and count our members, but some how I don't think the OP is willing to spend that kind of time. And if your not willing to spend time actually learning about the orgs your trying to compile than WTF we are you doing?
It's not like knowing the team size will be a predictor of success. There are countless factors that go into a success of a game dev org.
If you want to pay me to help you do this research I'd be happy to talk and negotiate a rate and hours.