This could be tough to find (for cheap), depending on the color of your seats. I found some black ones for $300 on eBay here.
But for $500, you could get custom seat covers from MRT
. You have a few more style options and many more color options there. While I don't have the seat covers, I've talked to the guys there about them and they are very knowledgeable and helpful, if that is the way you decide to go.
There may be cheaper ways, but I haven't been able to find them...good luck!