Also bought a pack of the Costco towels to use in the engine bay, door jambs, interior, wheels, etc...
They don't scratch on clean paint (or a CD for example), but because they have very little nap, any kind of dust or dirt could end up scratching your paint when wiping it down. Higher quality towels with thicker naps tend to provide more padding against the paint and have superior grabbing capabilities. These Costco towels are relatively poor quality, but this is a fair deal at 12/$8. Don't use them on your paint, but not a bad idea as throw aways for other jobs. The most plush and thick MF towels can go for over $5/each for a small towel, and perhaps more for something like a large drying towel.
Just because a towel does not scratch your paint, it does not mean the process of wiping won't. Generally this is why I advocate blotting rather than wiping with drying your car. You will become faster the more practice you get with your Elise, but at some point it comes down to priorities and which color you picked. How much do you care about faint spider webbing and swirl marks over the course of a year? Maybe your paint doesn't show much of it anyway.
If you want to use store bought MF, I know Autozone had Turtle Wax brand packs that come with one yellow and one blue. Decent towels that you could use anywhere on your car and have avg. nap. Sometimes I'll use one of these to remove a more stubborn glaze, as it has a bit more power than a super plush MF towel. San Diego has a detailing place called Rightlook on Miramar road.
Otherwise, stick to your online retailers.