Try a video showing at a nearby bar or in your own living room. There's always something you can do. Remember, what you are trying to do is create presence for Mumia Abu-Jamal in your workplace couture. That presence consists of awareness of Mumia, what he represents and the threat facing him. Awareness is the basis on that we wish to build concern and on concern a sense of urgency.
Consistency is key.
Keep working to put the issue forward. Don't give your co-workers a chance to forget about Mumia. Don't let a month go by without some kind of activity or leaflets. You will find that people come to you to when there is something in the news about the case. They may have questions, or want to argue, or they may just be checking in with you to show that they are concerned.