Cardio exercises with a broken shoulder?

This past weekend I had a bike wreck and fractured my scapula (shoulder blade). I have an appointment with the orthopedic doctor later this week to discuss the extent of the damage and treatment options, but I was wondering if I could get some ideas of cardio exercises I could discuss with him that I could maybe do in the interim. I was in the final legs of training for a half marathon in November and while I will in theory be healed in time for the run, I am obviously losing out on a considerable amount of training time. Walking is the only thing I can think of. Stationary bike might work as well as long as it doesn't have a seat back.

I am not in a cast, sling only and it looks like that will likely be the case after the doctor visit (fingers crossed).

Any ideas are welcome.