Try a walking stick or poles. A walking stick is helpful for balance, especially for older people. This is like cross-country skiing without the skis. When you step forward with the left foot, the right arm with the pole comes forward and is planted on the ground, about even with the heel of the left foot. This works the muscles of your chest and arms as well as some abdominals, while reducing the stress on your knees.
Many poles are now adjustable.
Use hand weights, but carefully. Hand weights can boost your caloric expenditure, but they may alter your arm swing and thus lead to muscle soreness or even injury. They're generally not recommended for people with high blood pressure or heart disease. If you want to use them, start with one-pound weights and increase the weight gradually. Ankle weights are not recommended, as they increase the chance of injury.