Do you want a freestanding tub in an alcove or an actual aclove tub?

Maax is a good source for tubs. You can order them through a big box retailer.

https://maax.com/bathtubs/all-products?selected=productlookups.installationtype.internal_value.Alcove

Just remember to check the water overflow height because that will tell you how deep the water can be. The tub can often be 22 " deep but only hold water to 14 -15 inches. Bummer.

An alcove tub REQUIRES an integral tiling flange. If you are going to make it do double duty as a shower, you will HATE having to step over a high sides tub. It’s unsafe, and needs grab bars to even begin to be non lethal. If it’s primary duty is a shower, look for a regular height model where the overflow it at the top of the trim. It won’t be perfect for a tub, or a shower, but no combo anything does both well.

Whether you are doing a drop-in soaking tub without shower, or a tub/shower combo that requires a tiling flange, look at Kohler Underscore. Good water depth without too crazy high walls.

Look for the water depth information while shopping. Often only found in the "specifications sheet" pdf. Kohler Greek has 17 7/8" water depth (one of the deepest available) and is 48" long. The compact length means you recline with bent knees. It's an ergonomic, relaxing position, your head naturally stays above water. The greater soaking depth means you can relax with water covering knees and chest... at the same time! The 48" length also leaves space for a shelf behind your head or whatever is most useful to your specific layout. I'm 5'7" and find it very comfortable and have seen reviews that people over 6' tall also find it comfortable.