See question for answer. (This is at the top of the unanswered list)
Otherwise I found the answer during my investigations in a blog post on elixir-lang.org
For the most commonly used records:
defrecord :xmlElement, Record.extract(:xmlElement, from_lib: "xmerl/include/xmerl.hrl")
defrecord :xmlText, Record.extract(:xmlText, from_lib: "xmerl/include/xmerl.hrl")