The Economy light fares are bookable through any channels (not like the Flugzug BSL-ZRH, which is only available when booking directly through Swiss and "offline" travel agencies, but not the more known "big" players like Ebookers, at least not available through their online booking mask) as much as I'm aware.
Are you holding any *G status? In that case, you could book without worries, as any *G gives you a free piece of baggage even on the light fares.
Otherwise, maybe give the travel agency a call might be easiest. I do fear that those fares are indeed Geneva light fares.