Rewrite to add a trailing slash, but independent of domain?

I'm using Apache and mod_rewrite to rewrite URLs for my web app. You can see it here:

RewriteEngine On
RewriteBase / 

# www. to non-www.
RewriteCond %{HTTP_HOST} ^www\.(.*)$ [NC]
RewriteRule ^(.*)$ http://%1/$1 [R=301,L]

# Redirect non-existant files so there's a trailing slash
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_URI} !(.*)/$
RewriteRule ^(.*)$ $1/ [R=301,L]

# Send the URL to index.php
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{RE开发者_StackOverflowQUEST_FILENAME} !-d
RewriteRule .* index.php [L,QSA]

All working fine, but the problem is the trailing slash rewrite. It works when I'm at the root of the domain, but in my staging environment I'm running this app within a subdirectory. I'm having to modify the RewriteBase directive to include the subdirectory or the rewrite fails.

I'm looking for a solution that will add a trailing slash to the URL - regardless of whether the app is running on the root of the server, without having to change the RewriteBase. Thanks in advance.

After poking around and some help by @MortBM, looks like the below works well:

RewriteEngine On

# www. to non-www.
RewriteCond %{HTTP_HOST} ^www\.(.*)$ [NC]
RewriteRule ^(.*)$ http://%1/$1 [R=301,L]

# Add a trailing slash to any non-existent files
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_URI} !(.*)/$
RewriteRule ^(.*)$ %{REQUEST_URI}/ [R=301,L]

# Send the URI to index.php
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule .* index.php [QSA,L]

Summary: removing the RewriteBase, and using %{REQUEST_URI} within the redirect did it :)