I have been a member of the Clyde River Steamer Club for nearly 40 years, and they have a very comprehensive collection of steamer photographs.
They offer a selection of a couple of dozen photos to members about twice a year and you certainly don't have to pay that sort of money for a postcard, plus two magazines come out yearly with your subscription of £17.
They cover turbines, car ferries, and of course paddle steamers. Sandy