There are many different alternatives to a cuff or penis sheath. The alternatives for women are various penis rings, cock rings and dildos in different shapes and sizes. A penis belt or a strapon dildo with a penis ring for women can also be an alternative.
For men, alternatives include various pocket pussies, glans rings, pleasure pussies, masturbators, penis pumps, adjustable penis rings and sex dolls. They are ideal for masturbation.
With a lot of hard work and inspiration, you can even make a penis sleeve yourself. However, you should avoid harmful materials and sharp edges so as not to injure yourself or the receiving part.