I just had a look around the Triumph USA website. It seems that they recently updated to include a bike configurator. Pick the Bonnie you want, the color you like, then you can add accesories... like the little leather tankbag you're interested in.
The configurator will add the accessories you've selected to the image. You will then be able to view the bike with tankbag installed from either side, and zoom the image for a better look. Hope this helps.
Triumph Configurator...
http://www.triumph.co.uk/usa/configuratorPopup.aspx