One selection of parts; no lever:
http://www.sewingpartsonline.com/bernina-707-sewing-machine-parts.aspx

Bernina take-up levers
http://www.mysewingmachineparts.com/bernina-take-up-levers/

England source; no lever:

http://sewingparts.co.uk/machines/bernina/bernina-707.html

Did have a used one
403-527-7801. Or [email protected]

Try ebay under sewing machine parts.