This DIY lightsaber is very well made. According to the person, he took 2 months to finish this project. The details are carefully built, including a crystal to “power up” the lightsaber.
It even has the swinging sound when you move the lightsaber around. And the tube is actually detachable. Of course, I know you wanted a retractable one. That is not possible. Here is another shot without the tube.
Nevertheless, take a look at the end product.
Want to make one for yourself? He has documented most of the steps.