Well, when looking for this kind of fanfiction, keep in mind that the quality can vary greatly. Some might focus more on the relationship building up to the marriage, while others might jump right into the married life. You could also try reaching out to other fans of the characters directly, perhaps in fan forums. They might be able to give you more targeted suggestions based on their own reading experiences.
One way to find such a fanfiction is to join relevant fandom groups on social media. There are often discussions about different fanfictions, and someone might be able to point you towards a story where Peter Parker and Cheshire get married. Also, check out Tumblr, as there are many fanfic enthusiasts there who might have come across or even written such a story.
I'm not sure of a specific fanfiction on this, but you could start by looking on popular fanfiction platforms like Archive of Our Own. Just search for 'Peter Parker x Cheshire married' and you might find some great reads.