I doubt you will find them for sale (but Jack might know a stall at one of the markets), they are so small and tend to soften very soon after picking. We are at about 900m on Flumserberg and have loads of them growing wild right now, both on our land and along the wanderwegs.

We picked lots this weekend and ate them straight away. I doubt there will be many left at this height by the coming weekend so you may need to go a little higher.