Done! The buttons were in my button stash, from where or when I am not at all certain, and the yarn is Cotton Fleece from Brown Sheep. I used exactly 2 1/2 skeins (250 grams- exactly!) on US size 6 needles. The original pattern is from The Knitters Almanac by Elizabeth Zimmerman. I knit it for a toddler rather than an infant.
I'm not entirely certain of the proportion of this sweater, I need a toddler model to try it on.
...and since he hasn't been seen in a while, here is Ollie, keeping an eye on things.