If you currently have a shower with just a rod and curtain system, you should consider upgrading to a glass door. This article explains the perks of installing a glass shower door kit, and what you need to actually handle the installation.
Shower Door Kits
Most precast bathtub basins are universally sized. That is, they generally are about the same length. This means that you can invest in a shower door installation kit that should fit your tub basin and includes just about everything you need for the project.