I'm looking for some financial assistance in getting a tub converted to a walk in shower. Are there any assistance programs?

Others have asked a similar question; these answers might be of help:

https://www.agingcare.com/search?term=assistance+for+bathroom+conversions

Until you can get the tub converted to a shower, you could at least get a shower chair, the kind that extends outside the tub. that way, you can sit down outside the tub, swing your legs over the side of the tub, then slide over in the chair. If you are able to shower standing up, you can then stand and shower. Alternatively, you can do most or all of the shower while seated if you get a hand-held shower fixture. Those are easy to install in place of the regular shower head--can be used either mounted up high as a regular shower head or taken down and used as a hand held. In either case, make sure you have grab bars installed inside the enclosure and at the outside to help you stand and move safely. the hand held shower heads are not expensive, and neither are grab bars though you'd need to get someone to install them for you. (I did the shower head myself. I'm a senior and don''t considier myself a very handy person!)

Call your Area Agency on Aging. They might know of an organization that could help you.