A designer for a paysite you can find anywhere.
How much it will cost, will depend on yourself.
I know designers who are willing to design a whole website for $100, at the same time you can also head over to
http://www.sevenedge.be and pay $10.000 for only the PSD file (unsliced)
Decide what your budget is, tell us your budget and we might be able to refer your to a couple of designers.