I don't have a 504 plan but try speaking with the professor. Maybe you can have you're presentations one to one. I remember taking public speaking in college and having a presentation every week. In the moment I extremely hated it and would dread Friday's. Especially when the professor would critique you and your fellow classmates also. I did practice in the mirror a lot (I mean a lot). Many of your classmates will also struggle since public speaking isn't something people enjoy. In the moment its going to suck but just stick with it. It's only going to help you in the future. If I can do it, you can also👍