when I worked in pharmacy there were 2 types available, a basic "sheet" quite thin, no elastic etc. quite cheap (around $10-$15)the second type was a thicker, longer wearing one with elastic to hold it on, around the $30 mark (from what I recall anyway...)
My supervisor used both types with her DD's, started off with the cheaper ones then ended up going to the more pricey one.
would it beworth checking out clark rubber or something similar to see if they have anything the same?