Assuming that you've got a QVGA device (320x200), then no such downsampling filter is available. You'll have to live with that black area at the bottom. You can bind and use the 'zoom up' and 'zoom down' actions.
@knakos,
the shaded fonts in Touché are quite hard to read whilst using a QVGA device (240x320), is it possible for me to somehow replace the in-game font to something more legible?
(some DIY font sizing would be nice if replacing font is a no-go)