If you can't ride in and have the seat "custom" fitted to you, why pay the price of a "custom" seat?
If your stock seat is close, find a local auto upholstery guy and tell him what you want. I'll bet he can get it pretty close, and not cost you $500+.
I bought a "custom" seat from Bill Mayer. I sent it back three times, at my expense, and it never was much better than the stock. Better yes, but not for the money.