Considering vBulletin 3 doesn't have a sidebar function, replicating it directly isn't possible.
We'll take adding it somewhere else for vB3 and vB4 into consideration, though
You should, however, keep in mind that vB3 is rapidly approaching EOL (End Of Life) - I believe, but I'm not 100% certain, that when vB5 goes Gold, vB3 will no longer receive security updates.
You may wish to investigate upgrading to the new vB4/5 licence (the licence gets you not only all vB4 versions but also all vB5 versions, until vB6 is released) and upgrade to vBulletin 4 in order to maintain the security and integrity of your forum
Currently, vB4 is our main development platform. While we try to avoid this, technological differences between vB3 and vB4 sometimes make certain features vB4-only.