There are several different VR headsets on the market, and many different considerations if you want to purchase one for your department (or for at-home use). Some of the most important considerations include price and intended use; remember that most VR headsets also require high-powered computers in order to run the software and that those can be expensive. 

Currently the top contenders in the VR market are:

HTC VIVE

Oculus Quest 2 

Sony Playstation VR

Samsung Gear VR
 

For a low-tech foray into VR, you might consider Google Cardboard, which utilizes a smart phone instead of a computer. 

Looking for a tool specifically designed for physical therapy?
Infinadeck 
An Omnidirectional Treadmill (ODT) is similar to a typical treadmill, except that the user can walk in any direction. The Infinadeck reacts to the user’s movement, including their speed and direction, to keep them safely in the center of the deck. This, when coupled with a virtual reality headset, allows for limitless locomotion in a virtual world.