I did a note following my visit last year to Swiss Valais. It can be found in the archive using key words "Valais Cornalin Petite Arvine".
I am sure that it should be possible to find wine shops in Zurich and Geneva with a well selected choice of Swiss wines but you will need local advice.
I was impressed by the tasty and original wines made from local Swiss varieties, particularly Cornalin (red) and Petite Arvine (white).
Finally you should know that Switzerland imports an amazing selection of French, German and Italian wine and the prices are reputedly very competitive.