They have covers that are for indoor only and indoor/outdoor.
You can pick one up cheap at K-mart or you can hit some OEM catalogs and pay upwards of $260. (Mid-America, Ekler's, Corvette Central) You can probably also put "car cover" in to an Internet Search Engine and see if something else comes up.
I have a Wolf for my C5. It's an indoor. I think it ran me $140.
I need to get one for my 1963 at some point. It will also be an indoor but will be more cotton-based. I also expect it to cost around $140.
I look for softness, warranty, breathable, washable, & custom fit. There are a lot of good covers out there.
Jack