Can I get a retainer if missing a molar? I currently have braces. (Photo)

I currently have braces and i am missing a molar on my top right side. I recently moved and at my previous dentist he states that it was possible to get one without getting a implant due to cost reasons. I do not want my teeth to move into the open space but cannot afford a implant. The Current dentist i have gone to states this is not possible. I am waiting for a appointment for a second opinion now. Any recommendations?