I got a bunch of Premo from sunnydaycrafts.com recently.
They only have certain colors in the 1lb size and a few more in the 8oz size.
I don't think they make all of them in the big sizes, not that I've seen anyhow.
I did notice that the big blocks tend to be softer - a lot softer.
It's not an issue for me since I like my clay a bit softer, any I can always leech it a bit.