It’s more common in Japan, however you can convert the entire bathroom and make it water proof. This would in theory make the entire room a shower room, plus it makes it easy to clean the entire thing. More on reddit.com

My 1940s house has full tile walls (and ceilings!) in each bathroom in vibrant hues. While we still have tubs, if we were to switch them out for walk-in showers, we’d take the tile down to the floor and add glass doors or linen curtains. Perhaps something like this: More on reddit.com

I've helped build a dozen of these bathrooms in the past few years. Completely doable. Moisture is not an issue if you a) have a high quality fan on a timer b) use in floor heat c) bomb proof drainage system, ie Schlueter, kerdi, or wedi and d) appropriate insulation and vb on exterior walls. We also go curbless for the shower - not always feasible depending on the floor system, but a much cleaner look, and easier to clean. All in all, these details cost a premium, so don't cheap out on materials or labor. Expect to pay 2-3x what a standard 3 piece bathroom costs. For example, that wall hung toilet costs north of 1k, the showers linear drain is $400, and the cost for install of both those systems is quite a bit higher than standard. More on reddit.com

Option 1: If you don't have any more room to play with, could you move the door on the existing wall? Move vanity and toliet do and have a shower north. More on reddit.com