It has been scientifically proven that you can maintain your mass with just 1-2 workouts per week. I am pretty sure that you should be able to find one hour per week for training. What you can do, is do HIT training routine - it will allow you to have short workouts with really good results. The secret to maintaining your mass with 1-2 workouts per week is by keeping the intensity of the training.
If you will not train, there is no way of maintaining your muscle mass, as your body will start to get rid of the excessive muscle mass that is not employed.
During this time I would recommend to have just the basic supplements, and nothing special. Creatine, BCAA and perhaps whey protein. It would be great to have fish oil in that stack as well.