Never climbed in Chamonix, but here are some things that could help in general.
1. Take up solo aid climbing. You learn tons, you get to climb places you might never get to climb, it shows commitment. People are eager to talk with you if you look like you are having fun. Even if no one invites you to climb with them - in solo aid climbing EVERYONE is always having fun.
2. Climb with 50-somethings and older. They are survivors and they may like climbing with younger people. You might get more leads. You can learn tons from them. They could introduce you to people your own age after they get to know you.
3. Join a climbing club or a search and rescue team.
Wondering if you're still in the valley. I'm currently based in Geneva but come through to Cham often. I am always looking for a new climbing/skiing partner. I'm heading through this weekend to climb if you want to meet up, let me know. I would be interested to climb some ice if the conditions are good. Are you into that? Either way we could meet or get in touch about getting on the rock this Spring.
All the best,
I'll be in Cham later this month- anyone up for the ride? I've been going there since the 80s when the Biollay was the place to camp. That was turned into a bus park and there was the forest. Now it's all illegal. I'm planning to stay up high in any case to avoid the valley. I may have to check up on that one French gal from several years ago though..
I lived in Italy for 3 years and was always able to find partners up in the Cham area. Many Euros use summitpost to find partners and that is where I normally went - aside from the local forums that were around the mtns I lived near.
The suggestions above to join the French Alpine Club are solid - they usually have offices where you can hang out and find partners.
In town, there is also the tourism building as well as the head of the Alpine Club where there are bulletin boards.