Qtopia Search works well. You can get it at:http://killefiz.de/zaurus/showdetail.php?app=990
If you uncheck the usual magnify option on the icon it displays correctly in high res mode.
The only thing it can't cope with is that it has an option to view files it has found with a text editor. It tries to launch the text editor in the 320x200 resolution, and then fails to do so. The main app doesn't bomb, it just means you can't use that option on the menu.
Other than that, its pretty good.