If its just for keeping dust off your car inthe garage you can get the plastic car protectors from the body supply shops they are cheap and work great., Most body shops use them to protect stored cars from overspray and sanding dust etc.
But for outside these should not be used. 

Car covers are very specific for indoor or outdoor use. You need to be careful using the right product for the application my buddy used and indoor cover outside just for a short time, it rained and then got baked in the sun. Small micro bubbles appeared in the paint all over the place. It went from a #1 to a 10 footer.

So be careful and do some research.

Mike, I've bought a number of covers over the years as I'm one of the few people that would cover my car in the parking lot so it didn't bake all day.

Check out California Car Covers or Wolf Covers and get the lightest (Spell cheapest) cover they have that isn't plastic.  You should be able to get a cover made of Evolution fabric that won't scratch your paint and will keep the dust and light moisture off the car but won't sweat.  Never use plastic!!

You should be able to get something that works well for your purpose for around $130 for custom fit or quite a bit cheaper for OSFA.

For serious work you want a cover made of NOAH fabric.  I had Josh-Ka-Bob's 90 GT setting outside for two Colo winters with a Noah cover and both the car and the cover survived quite nicely.  In fact, I think Josh is still using that cover.  But that was over $200 five years ago.

BB

Well  I bit the bullet and bought a good one made of NOAH, spent about a hundred more than I had planned. Ended up being about $250 with bag and cable and lock. Hope it holds up good.  I should of bought a convertible top since I dont have one of those yet.  Just tired of all the dust getting all over the car and interior.