Anybody know where to find the fields available for a customer statement? I am creating a custom customer statement template.

Are you customizing either the Standard Statement or Multi-currency Statement templates? If you hit the big + (fields) in the WYSIWYG editor it'll show all the fields that are available in a nice grouped/foldered list. You can also look at the SuiteScript Records Browser to see what the standard fields are and what their internal IDs are.