Some of those window films work well.I have them in my dining room,because of the afternoon sun,i can see out,but no onecan see in.I had mine don by professionals though as it's such a big window.But if yours is small you could probably do it yourself.

My bathroom window is above the tub as well,but high enough that all you can see is anyones head,if they are tall enough.
kathi

My bathroom window is in the shower! It is a full sized window. I hung a white plastic opaque shower curtain, doubled with the fold facing the shower head, over it. I can move the curtain aside because the spring rod is the full length of the tub. We do also have film on the bottom half of the window, and a big shrub outside.

I would like some of those bottom top blinds too in various places in my house, but it never occurred to me to try to retrofit regular blinds. To buy bottom-tops new is quite expensive. If any one knows how to do it, I'd love to hear it. BTW, I have friends who have them, and its kindof a disappointment to realize that the strings that raise and lower the blinds cover the window all the time, so you don't really get an unobstructed view.

Excuse my going on and on, but you have got me thinking about mounting a shade onthe bottom and pulling it upwards which wouldnt work well in a shower however. But that would just involve one string up the middle of the window where we have a muntin anyway.

Good luck.
Kathy