If you want something similar (but not permanently installed) you can use Bridge Bone Beads from SouthCoast (same guys that make the strings.) You thread the string through the side of the bead and out the top. It goes onto the bridge, the bead acting as a stop. This makes restringing a breeze, is said to provide a less acute angle across the bridge, and if you change out strings, it makes it easier to restring again. I have a set on one uke and I like them. They are not expensive. The brown version is kind of cool--looking very folkloric and handmade.