themes/mytheme/page_template_foo.php // custom page template
themes/mytheme/css/page_template_foo.css // additional CSS
themes/mytheme/js/page_template_foo.js // additional JS
The code should be self-explanatory, but see the comments for explanations as to what’s happening.
Notes: this method increases overheads as it tests for the existence of files, if you’ve only got a couple of custom page templates, you’d be better off hardcoding. That said, if you’re using caching it shouldn’t be a big deal. Also, unless you’re using HTTP/2, you’ll probably want to use something like Autoptimize to concatenate the CSS and JS files.