Neo-angle showers are an easy way to save space in a tight bathroom. Measuring for a door though is really no different than measuring for one on a standard shower. The two main measurements you need are the height and width of the opening for the door. Also, try and purchase a door with a similar glass pattern as the rest of your shower, which will only offer cohesion.
Measure from the base of shower to the ceiling. This measurement will be your shower door's height.
Measure the with between the two pieces of glass that the shower will sit between.
Measure the distance form the front of the shower to the closet fixture in your bathroom. This measurement needs to be greater than the width of your shower do, ensuring that the door will be able to open fully.