This heavy gauge clear plastic liner is just right....the longer length ensures no shower water escapes, it doesn't blow against you during showering, and even without the little magnets at the bottom, the weight of the liner keeps it in place.  I couldn't find this size at any local stores, and the price tag with free shipping g makes this a bargain.  

Pros: Strong material
Cons: No magnets at bottom to keep it even better in place