What size bag are you looking for?
Any store that sells cake decorating supplies should carry them. If you're using icing, you can also use a ziplock bag.

Here is a link that might be useful: pastry bags on Amazon

WalMart here sells the clear plastic cone shaped ones....ones like you'd use for crafting food gifts such as cocoa and the orange jelly bean carrots.

I know that they are also at both AC Moore and Michael's (and you can use a coupon!)

After rereading your post I see you said 10" ones......I completely overlooked that!
Oops.

I believe JOAnns handles them.