The only entity with all (or most) of the information would be...

The only entity with all (or most) of the information would be the Automic. They have all the buy and sell transactions for each holder, but perhaps not the price of the trade. They would be able to cross-reference the transaction date to the share price range for the day to get an estimated average price for the trade. It might be worth sending an enquiry to them. They might have a bored data analyst sitting at a desk waiting for an interesting question.

The only other way I can think of would be to request a copy of the shareholder register. Any shareholder is entitled to do this. It will cost you a few hundred dollars, but probably less than $500. The register gives you the number of shares held by each holder, and their entry date. The entry date resets each time a holder sells out completely and buys back in. But if they never sell their entire holding, the original date remains in place. So any estimates you made from this data would require you to make all kinds of mad assumptions about average trading activity and so on, so you would really only end up with guesses.