First, to shout out, your sig length is over regulations and standards. Yours is over 600 pixels, limit is 500 pixels. Please change it immediately or I'll report it and the Admins will remove it personally (and possibly lock your sig for a certain amount of time).
And to answer your question: Have a Female Pikachu hold Light Ball, it's an item that 25%, or so, of all wild Pikachus hold. Then leave it at the Day Care with a Ditto. You'll get an egg with a Pichu that knows Volt Tackle.