I don't know of any ready made python css minifiers, but like you said css utils has the option. After checking and verifying that the license allows for it, you could go through the source code and snip out the portions that do the minifying yourself. Then stick this in a single script and voila! There you go.
As a head start, the csscombine function in .../trunk/src/cssutils/script.py seems to do the work of minifying somewhere around line 361 (I checked out revision 1499). Note the boolean function argument called "minify".
