With anything you ask for on an IEP, it's always the "is this the hill I'm going to die on?" Schools can, and often do, say no.
Then you have to decide if you have the data and documentation to proceed further. Or, just take care of this issue privately at your own expense.
Every family has different things to consider.
Here is more information on dysgraphia from one of our OT contributors who specializes in it. Link to buy her book on it is in the post I think: https://adayinourshoes.com/dysgraphia/