Perhaps the iTead Studios bare Duemilanove, MEGA 1280, or Nano 3.0 boards would be close enough?
http://iteadstudio.com/store/index.php?main_page=product_info&cPath=19_21&products_id=264
http://iteadstudio.com/store/index.php?main_page=product_info&cPath=19_21&products_id=411
http://iteadstudio.com/store/index.php?main_page=product_info&cPath=19_21&products_id=247
The DangerousPrototypes forum says that they had bare UNO boards but the link seems to be broken now:
http://iteadstudio.com/store/index.php?main_page=product_info&cPath=19_21&products_id=276