My dad is 84 and needs a walk-in shower, he is blind and is veteran, is there any assistance available for his walk-in shower?

Call Office of Aging.

Another vote for checking out a care home for your dad.

Contact a services for the blind agency in your area.

VA benefits for spouse of veteran who passed?

The VA does have a program that will make modifications to a Veteran's home. It may depend on his % of Service Connected Disability.
Check with your local Veterans Assistance Commission or call the local VA and talk to a Patient Advocate or a Social Worker.

While I am sure there is more than likely help out there for your dad getting a walk in shower, have you instead thought about allowing your dad to move into one of the VA nursing facilities where he will receive the help he now requires and can spend time with a lot of other veterans? That to me sounds like a win win for him and you, and the VA homes that I'm familiar with are actually quite nice.
Just a thought.

Contact the va, area on aging, 211, 311. Also American Legion and VFW.