export path to $PATH via shell script

Question

Is there some best practice of adding a path to $PATH via a shell script permanently via a shell script and have it accessible? I believe I have only seen temporary solutions, via export PATH=$PATH:<path/to/add> but suggested solutions like

echo "export PATH=\"<path/to/add>:\$PATH\"" >> ~/.bashrc

seem to add a "export PATH..." line every time the script is called. I am looking for something like this:

<install.sh> 
#! /bin/sh

new_path="/foo/bar"
echo $PATH

# set path variable
updatePath($PATH, new_path) <---- how to do this

#load path variable in current script
source ~/.bashrc 

echo "updated path": 
echo $PATH

expecting the following output of running ./install.sh:

/usr/local/bin:/usr/bin
updated path: 
/usr/local/bin:/usr/bin:/foo/bar

Any working solutions or best practices? I want to have the /foo/bar stored in $PATH permanently and accessible directly within the install.sh script as well as from the command line. Ubuntu 22.04.2 LTS