have you looked through the screen caps at David Tennant Fan? You have to be a member to view them, but all you need is an email address to register there, and they have quite a lot of caps, although due to age of the source material the quality isn't always brilliant.

That's the only place I can think of that even has a decent amount of them though. http://davidtennantfan.com/gallery/index.php

One other thought would be to actually ask von_gelmini if he has any pics he'd share. He has a thing for baby David so I expect if anyone has some good ones it's him, and he's a lovely guy so I can't see him saying no.