http://www.ebay.com/itm/Arcade-Card-Duo-PC-Engine-Hucard-Japan-import-/220928791135
Thought I would post this ebay auction for anyone looking for an Arcade Duo card. Seem like a decent price...$15.99 with free shipping.
I never dealt with this seller, nor do I have any affiliation.
wow I checked and it was 15.99. and then he ended up changing it to 34.99 lol