I hike in that very area some years ago. We would typically get water from the refuges.
Le refuge de la Balme
Le refuge de la croix du Bonhomme
Le refuge des Mottets
Il refugio Elisabetta
You'll find clean water there, and they are not that far apart (about half a day between each, I'd say).
The rest of the time, if you don't have enough ...
Probably your best solution is to take a small camping stove and boil water you get from a creek. The huts are basically doing the same when they sell you tea water.
In my experience, most bivoucs require you to bring your own stove anyways, so this method hardly adds any weight (maybe some extra gas). It is way cheaper than buying a water filter and it does ...
Back in 2014 I was climbing Ben Nevis, where the weather was relative calm on the climb. At the time, I didn't truly appreciate how fast weather conditions can actually change, so to my surprise, I was shocked when a heavy fog felt like it came out of nowhere and disorientated me. My tips would be:
Bring a camera with you, taking photos of quite obvious ...