The proble is that most of the Olympus (Zuiko) lenses are not as fast as their Canonikon equivalents. it's really hard to find a Zuiko lens with F 1.x.
Anyway, Leica have fast ones such as 25mm f1.4 but I guess this one is really expenisve or a Sigma 24mm f1.8 or 30mm f1.4
You may also fine more lenses for you camera on the following page:
http://www.four-thirds.org/en/products/lense.html
And finally, let me ask you. Do you want a fast lense to take photos at night or to shoot sports etc? Or you are into portraits and want a lense with shallow depth of field (bokeh)?
BR, Gr33n Data
http://www.flickr.com/photos/gr33ndata/