You could try using a rectangular cooler. A lot of people I know who only carry a few discs will use them. They usually hold a few discs, a couple drinks, and maybe a couple other items. Some companies make minimalist bags, too. I think Upper Park has a few and there is a company that makes a bag called a NutSac.
Infinite Discs, Dynamic, and some of the other big companies also offer smaller casual round sized bags depending on the style you're looking for. A lot of them are very affordable.
Fair enough, depending on where you are at, a flat bottomed style backpack may work well for you, something like: Cargo Style Backpack