Unless /directory/cgi-bin/scriptname/script.cgi is not actually a cgi directory you can't. Webservers (afaik) won't serve you the file, it will only serve you the result of running the script.
In short, you can't. (at least it doesn't appear likely)
Well, to make it explicit: 1) because it would be a giant security hazard to allow anyone to just download copies of running scripts and 2) because you can make a file either executable or downloadable, but you have to choose one or the other.