I have done the same thing and here is the css that I used. I used the same code from twitter as you did. The styles from this will not be the same as you need, but you can change the font sizes and things to suit.
This code covers the div styling itself, the ‘follow me’ link at the bottom, links in the tweets, the tweet text and background, and the header of the box containing everything.
I have found that sometimes, when I tweet long links, it spills over the side of the box. I’m pretty sure if you take away the width of the ‘twitter_div’ and give the sidebar div a fixed width, that links will automatically break to the next line if they need to.