That is not just a script, that is a whole solution. There are several products that is made out of FileMaker, but I doubt noone would give away many hundred of hours just for free. FileMaker can handle all those things you ask for, but you or a consultant for you need to build it.
If you need help getting started to build a FileMaker solution, first learn FileMaker for free with FileMaker Training Series
Here is a link to things that people have made in FileMaker
Yes "whole solution" was my first answer. You might also search 'filemaker POS' in your favorite google.
There are several really fine solutions!