Help with safely bathing for disabled senior. I have fibromyalgia, am obese, osteoarthritis and need a knee replacement.

Contact social services for your county or your local Area Agency on Aging for resources.

What about hiring a bathing aide?

The standard advice here is to call your county and try asking churches or Nextdoor for free help. If what you are asking for is a couple grab bars in the bathtub, you can probably find a volunteer or very low cost handyman.