I did it again - got part way through with a project and ran out of yarn. To top it off, the store (JoAnn’s discontinued the line! I’m looking for Sensations Rainbow Classic Pattern in Blue/White Stripe. 2 or 3 skeins. Willing to purchase or trade.
Try Ravelry’s stash list. Good rule of thumb is to buy more than you need. 
You can then return it if you don’t need it or do as I do and keep it in stash and later make a striped project.
Thanks for the hint on another place to try. I always do buy more when I know what I’m going to make. I pulled this from my stash to try a new pattern, not realizing it would take more yarn than I had.
I don’t know what you’re making, but sometimes you can use another color of yarn for part of it as contrast. You know a stripe on a hat or the sleeves of a sweater, etc.