Cowcorn is a large enough city to have a specialized pajama store! Navigating there with the carriage is a bit unwieldly, but Haroun knows how to stick to carriage-navigable wide arterial streets. He's home now.
The pajama store does not have quite the selection of such Earthly clothiers as Isabella Swan was once accustomed to shop at. She can choose between Pajama Style 1, Pajama Style 4, or Pajama Style 6, if she wants to immediately wear out something in roughly her size. One ordinarily has pajamas custom-tailored, which takes a few hours even for a high-level Tailor. Haroun looks abashed for not realizing this earlier, and suggests that if Bella wants to upgrade to magical tailoring, she can get some nice magical pajamas by paying gold instead silver.