Either way I doubt you’d be able to get them. They’re part of Chris’ branding and releasing the current design for free or for money will only de-value his branding he’s made for CSS-Tricks and his own site.
As Andy says… the css-tricks theme is likely not for sale. However, you can see how Chris makes themes with his book at digwp.com. You can also get some themes there that I assume are his (or maybe his co-author’s).