Upvote:2
As pnuts said, you should try the RELAY at Grenoble airport.
If there's no SIM card there, try the bureaux de tabac in l'Alpe d'Huez. You should find a SIM card there.
Upvote:3
GNB has a newsagent (RELAY) that just might be able to help. However it might be worth checking first, the company can be contacted via Facebook.
A more promising alternative seems to be ALPEDHUEZNET which can be bought on line.