Yup, Target or and Auto Parts store like Kragen. I've had luck at both. A soft nylon bristle brush works great. Our seats are due for it, too. We've got one new cushion that's making the others look filthy.
I bought a vegetable brush, yes veggie, on the recommendation of a boat detailer and it works awesome. It's just stiff enough to clean the vinyl but soft enough to not hurt the stitching. Found it at Walmart for a few bucks.