i redid mine over the weekend, only because a friend had a cover that would fit it. i didn't buy it, but i think he said it was around $40.
if the foam's ok, the cover's dead simple to do, took about half an hour and looks 100% better. there's basically little triangle hooks cut out of the seat pan that you can jab through the material then bend them back down. didn't bother with the brads as this is only temporary till the race seat is uppolstered.