Benev brand Pure Titanium Dioxide.
I bought this recently because I battle with finding a good SS that doesnt break me out. I have found a few, but wanted something I could wear day to day at home (when not going to be outside) for incidental exposure.
This fits the bill. 2-3 drops mixed with any moisturizer gives you a physical block of spf 30.
It does leave a little white cast, but it is fine for me at home (I work from home). I would add some of my SPF tinted moisturizer by Clarins if I was going to go out.
I just add a few drops to my Burt's Bees Pomegranate Daily lotion and it is great.