Can an ER doctor order an MRI or does that order need to come from your family physician or specialist?

My husband left the ER Wednesday with discharge papers telling him to call his doctor if symptoms continue. The ER doctor told Jon he would need to follow up with his doctor and the next step would be an MRI. He is having neurological symptoms that are keeping him from functioning properly. He was told it was possibly nerve inflammation. He can’t go back to work until this is resolved.

Our problem is that Jon does not have an established doctor. We finally found a doc accepting new patients (that was a struggle) but they can’t see him until Thursday. Jon can’t wait that long. His symptoms are at their worst today. Worse than they were on Wednesday when he was transported to the ER. Do I just watch him suffer for four more days before we have a doc tell us our next step is a specialist, then wait another week?!

Where do we go from here to get the help he needs without a family doctor order?