Check out this glass block window manufacturer.

Here is a link that might be useful: Hy_lite Glass Block

We had this problem with our bath remodel last year. Our house was also built in the 60's and has windows in both showers that were rotting. We had to do a complete, to-the-studs remodel to fix the rotting studs which resulted from moisture getting in from this window.

Our solution was a vinyl window with obscure privacy glass with grilles between the panes to be as consistent as possible with the look of the other windows from the outside. It's also safety glass for code purposes.

I've attached the frightening before photo - you can see we had to have blinds in the shower! I'll post the after photo in the next post.

Here is the after photo showing the replacement window with the privacy glass. We've done many experiments with someone standing in the backyard while another showers to make sure you can't see more than you'd like, and this solution has been great.

We had a window in our 1920 house that was probably originally over a clawfoot tub without a shower. We replaced it with one that was shorter (low edge is now about shoulder height). We'll either put an obscuring film over it or hang a stained glass window, though it's now high enough that privacy isn't an issue.

We've got vinyl siding on the exterior, so it wasn't a big deal to close it up.

Before/not-yet-after photos: