I think a Citizen with Duratect titanium would be fit those requirements well. Lightweight because it's titanium, and durable because of the duratect treatment (more scratch resistant than stainless steel) and quartz movement. Two examples are:
Air diver line (PMX56-2811 pictured):
Promaster Land (PMD56-2952 pictured, but more than $500):
Air diver line (PMX56-2811 pictured):

Promaster Land (PMD56-2952 pictured, but more than $500):
