Can I get aid to get my disabled wife a walk-in shower?

The Disability Gov site has many suggestions for financial help in making a home accessible. https://www.disability.gov/disability-can-get-help-modifying-home-make-accessible/

If you are a veteran a possible source of help is listed for that situation.

I wish you success in finding some help. Please let us know what you discover and what worked for you. We learn from each other.

It is possible. Is your wife on Medicaid? Does she receive social security benefits? If she is already in some program discuss this with her case worker.

Also call the Disability Help Line in your county. Explain the situation and ask for advice. They may know of local organizations that help with these kinds of accessibility improvements.

No, capital improvements are solely funded by the homeowner