It depends by what type of Spider-Man series you mean.
In the movies, he got it tailor made. After his wrestling match The Flying Dutchman thanked him and told about his brother who was a tailor and would make him a costume if he ever went on to become a prefessional wrestler. So Peter went in wearing his wrestling outfit as a disguise and showed the trailor drawings of his ideal costume, the tailor made two of them free of charge. One was trashed in his final fight with the Goblin.