How can I get a copy of my father's will?

Ask the girlfriend for a copy; if she will not give it to you, ask the Uncle if he has a copy or knows which lawyer prepared it. If none of that works, tell the girlfriend you have no choice but to file to probate the Will and perhaps contest it. If you file, the executor/executrix must file the original of the Will with the Court. Realize however, that your father had the legal right to disinherit you so you may have no legal basis to challenge the Will.