Yes, you can do a walk in shower with this size bathroom. There are probably several configurations, but it depends on the location of your doors and windows, etc.
Can you post a floor plan?

Found an inspiration photo with walk in shower where the overall bath dimensions are similar to your bath. This bath below is a 5' x 12' bath. Hover to expand photo and click on the photo name for details


This bath is 4'9" x 9' and has a walk in shower as well. All the details can be obtained by clicking on the photo name


This bath is 7'11 x 5'2" with a walk in shower. You can do a modification to get more features in your bath because it is much larger. :)


One more for you: this shower is 40" x 54" and the overall bath dimensions weren't specified but appear to be within your specs. However, there is a tremendous amount of helpful info for you if you click on the photo name and read the comments.

A walk-in shower is merely door-less. It can be large or small and you should easily have the space to accommodate it with actual walls or just glass for a divider. When space is tight, the type, placement and direction of the showerhead will directly affect the splash factor. Be generous with your waterproofed walls adjacent to a smaller walk-in. If you really want a larger vanity in your space, you could consider the euro solution of a wet room.