You can get silk scarves in alot of retail stores these days. I got given a lovely one for my birthday, from cotton on. Also places such at the tie rack (think that's it's name) usually have a good range.
Just remember to check the label to see whether it's silk or not.
I did give it a go awhile back but never figured out a way to get it to stay on - i'm a restless sleeper most of the time.
In terms of satin pillow cases you can get them at spotlight in a pretty decent range of colours.
I've found in the past that I get less frizz and my hair seems to stay cleaner (weird) with satin pillow cases, but I have a nightmare of a time trying to find one for my favourite pillow (u-pillow, banana pillow or other various names)