Joe Check out this thread. This should provide some details about preferred hardy lilies.
http://www.pondboss.com/ubb/ultimatebb.php?ubb=get_topic;f=15;t=000025#000000

http://www.pondboss.com/ubb/ultimatebb.php?ubb=get_topic;f=15;t=000016;p=1

http://www.pondboss.com/ubb/ultimatebb.php?ubb=get_topic;f=4;t=000040#000004

Come back and ask some questions if you still need some more advice especially about some specific names of varieties that you are able to buy.

aka Pond Doctor & Dr. Perca Read Pond Boss Magazine -
America's Journal of Pond Management