Is it possible to have a reasonably soundproof sliding door to a bedroom?
If you have the money there are some fantastic barn door style sliding doors made of solid wood that should give you better sound deadening than a normal hollow core interior door. 

Any door made of solid wood or even foam core doors will perform better than glass or hollow core doors as far as sound deadening is concerned. The thicker the better. 

Pretty is one thing but practical is another. I think solid wood does both.