Citadels Online

http://citadellesjavagame.free.fr/

Check this out. This website allows you to play the card game online. However, the game will take some time to load using Java. Anyway, it is a cheap alternative compared to going Mind Cafe.

http://www.fiade.com/citadels/

This website offers the game for download. It actually provide the cards in jpeg format. If you have lots of ink, maybe we can consider DIY Citadels.

http://cgi.ebay.com.sg/Brand-New-Citadels-Card-Game_W0QQitemZ270200724816QQcmdZViewItem

This is the best option. Get the card game for S$35.