This is not quite so high, but is easier to get on/off than the Tadpole trikes.
http://www.greenspeed.com.au/anura_main.html
(I know that's an australian page, but they aren't too hard to get in the US).
If money isn't an option, a similar trike
http://www.bicycleman.com/recumbents...ent-trikes.htm