I build the device into electrical tubing (25mm diameter) which makes a housing which is stable and can be carried around easily, is just big enough to hold a 18650 cell and is very cheap. I added an off-the-shelf LiPo charging board and some cable with a robust connector. For the prototypes the lid (with the USB connector for charging) was manually cut from acrylic and the other end I just sealed with silicone. The circuit for a latching switch, a mode switch and to determine the length of the LED strip was build on perfboard and connected to an arduino nano clone.