Where are you located?
Try here..
Our selection of 195/50 15 - tires-easy.com
I suggested that size because i can buy them off the shelf at NTB, PEPboys, Firestone, and sears in my local area. (I dont' run that size currently. And I don't buy my tires there).
IF you say there are none for your geographical location, I am going to go ahead and say you need a separate set of snow wheels and tires. In the long run you get better performance in both seasons, and the "partial" use will allow tires to last longer.