Bring some really thick, heavy resistance bands. They'll fit in your bag easily and you can replicate most dumbbell and cable movements with them if you have the right setup. You will at the very least be able to maintain muscle with them, especially when combined with body weight exercises.
Bodylastics is the brand I use when I do band workouts, check them out. Not affiliated with them, just a customer.
Bodylastics is the brand I use when I do band workouts, check them out. Not affiliated with them, just a customer.