Local craft stores are beginning to catch on to the new trends in party supplies but if you're looking for paper straws or striped twine, you will have to shop online for now. Here are a few of my favorite online party supplies shops.
I have also used Etsy for party décor. Party City is still a great resource but may not always have the exact color you need. I have had luck finding the extra large balloons there but they only come in a variety pack with specific colors. If you're looking to order a specific color, online is the way to go. (Party City will fill your balloons with helium for a minuscule charge).
Hope that helps with your party planning needs!