Criminal Law Issues: How Can I Obtain a Certified Police Report for USCIS After My Case Has Been Expunged

Back in 2015, I was arrested and charged with a third degree battery charge. However, my case was dismissed and I was found not guilty. I also had my case expunged shortly after. Couple days ago, I and my husband had an interview with the USCIS regarding my application to register permanent residence. (he is a citizen) The interview went well ( at least that's what we thought.) She (USCIS officer) collected some of our pictures, bank statements, and phone logs. She also kept the court disposition, in which specified that the court has no record of my violation. However, the officer required us to provide the certified police report for my arrest in 2015 in order for them to process my application. My case has been sealed so no place has excess to my file anymore. Therefore I cant obtain my police report either at the police department in the city where the arrest took place or at the courthouse. What should I do now? Do I have to have my case unsealed or just have the police department written a certified statement in which states that they have no record of mine?
Thanks

Criminal Law Issues: How Can I Obtain a Certified Police Report for USCIS After My Case Has Been Expunged