A nice light titanium frame, not too small. With polycarbonate reactions or transitions lenses.
The polycarbonate, is about 30% lighter than std lens. So whole thing very light. Will stay put nicely.
Speccies have free reactions at mo. polycarb and anti reflect is £40
Titanium frame £125 so £165 total.
Or go super cheap, £69 frame free reactions total £69.