How do you make an existing variable (from a module) available for use in my__node.tpl.php? D7 The contrib module i'm using (media gallery) outputs a block with a single thumbnail used to trigger a lightbox gallery.

The module has a tpl file used to render the thumbnail.

I want to isolate the single block thumbnail image ($media_gallery_item used in media_gallery_media_item_thumbnail.tpl.php) and insert it directly into a new node template (node--media-gallery.tpl.php)so that I can float the image in the body field (and preserve the lightbox trigger).

This is my first attempt at using a preprocessor.
Incidentally, I posted in the modules issue queue two weeks ago. I'm posting here as well to hopefully get a quicker response.
The only variables different template files have in common are the ones returned from template_preprocess(), or hook_preprocess(). See also _template_preprocess_default_variables(), which defines the default values for some of those variables.