I want 🤤
Then you'll have to get a team member to dig it up for you. I no longer have access to the relevant board. IRC though it was pretty easy to do.
The basic theme wrapper is a piece of cake. That's just a div with a 1px grey border and a bit of border-radius. Some of the internal detailing was a bit trickier, if you want an exact match of all the original gradients.
The category/title header bars and the post backgrounds are as easy as the basic wrapper. They're only a few classes, and you just use border-radius instead of the extra spans, etc. The spans can be either set to display: none; or left with default sizing and positioning, but set to no background.
It is possible that the code in question may have made it into an early 2.1 alpha build, but I can't remember whether it did or not.