A place within WordPress for non-WordPress scripts?

For every kind of file that isn’t part of the WordPress core code, there seems to be a place for it in WordPress — such as a place to put extensions — and a place to put themes.

However — is there any place in the WordPress file-tree where one can place PHP scripts that aren’t really part of WordPress at all but still need to be included within the WordPress file tree for the sake of URL convenience?

For example — a very simple PHP script that redirects the browser to a wiki that is *related* in *mission* to the specific WordPress project — but needs to be able to be linked to through a URL that is within a domain at who’s root directory sits WordPress.

Any answers would be appreciated. Thanks.