In our last house was one of those plastic tub/shower all-in-one-piece deals. Hated it. Now, we have a shiney porcelain coated steal tub. Beautiful. I understand why you're looking. Hope you find it. I can't imagine why that's difficult to find???? We use a rubbermaid bath mat, so nobody's slipping.
Have to be careful about that mat. Tends to retain water and germs under it.
I clean my tub and mat with a solution of vinegar and dish soap, then stick it on the tile above the tub.
Another thing: Those nonslip tubs are like sitting on sandpaper, mighty unpleasant.