Modify html code in archives widget

The Archives widget produce html code like this:

<li id="archives-3" class="widget widget_archive">
<h2 class="widgettitle">Arkiv</h2>
<ul>
<li><a href='link' title='February 2011'>February 2011</a> (5)</li>
</ul>

If would like to change

<li> to <li id="some_id">. Is that possible without modifying core WP files? I’ve searched for archive plugins with no success.
I know there is a way to alter that list tag, by using CSS for the tag itself, but that would include all other list tags too.

(I want this to have custom list image bullets for different widgets. See my blog for an example, where I have managed to get it working for all widgets but the archive).

http://springforfan.se/