All a flash card is is just a paper card with a note on one side and the name of the note on the other. We use them here in elementry school, for teaching math problems or letters to kids, and musical notes. You just flash the card and figure out the note. If you get a hold of a begining keyboard music book that has large notes with the letters next to them you can just copy those notes onto a index card. Or ask someone in the music department at you local collge or university they can help you out.
Also check out eMedia's Learn to Paly Keyboard Pack ($169.95 US). It's a computer- assited learning porgram for mac and pc that teaches you not only how to play but also how to sight read. Taught by a former Julliard instructor.
http://www.emediamusic.com