You'll be hard pressed to find something that is completely waterproof, but water resistant is pretty easy to come by.
Here are mine from Coverking.
Mine are for Mustang buckets, but they do sell them for FSBs. $200 will do both buckets(with the arm rest), and another $200 will do the rear bench.
They have the neoprene ones(similar to Wet Okole), but I opted for the faux leather. I like the way it looks, and they're easy to clean.
If you have a checker, schucks, or kragen in your town, you can check out the instore display, for the different fabrics, and colors. Mine took about 2 weeks after I ordered them.