I don't know the exact changes you'd need, but maybe I can help you get on your way.
Take a look at /templates/pathbar.tpl. This is where the search functionality is added if enabled. Copy that code into which ever file it's needed under the Siriux layout, probably albumBody.tpl and singleBody.tpl. BE SURE TO READ the instructions at the top of the files before editing. You'll need to create a local diretory under /layouts/siriux/templates so you don't loose your changes on an upgrade.
FYI, the layout/theme system for G2 will be changing in the coming weeks. It will be released with B4, however, I wouldn't be surprised if it starts popping into CVS on the nightlies before the Beta is released. It should make these types of changes easier. However, it will make your changes invalid.
EDIT: again that's just an FYI so you're not surpised if your changes are broken on an upgrade.