You already have "rims" on your car...that is the part of the wheel that the tire mounts too. You also have center sections, and hub pilots...but I am sure that is too technical.
If you really want to buy aluminum wheels check out
www.discounttire.com They are an independent dealer for all kinds of wheels and tires.
If you want to buy used check out Craigslist.
If you want new wheel covers (previously referred to as "hubcaps") go to Walmart and pick up some spinner hubcaps, they are the bomb.
Or if you really want to be cool get some chrome spraypaint and paint on some tri-spokes (that's what I did when I lost a wheel cover on my Bentley Arnage)