I maybe not dark ones, but I noticed twixanddud has some tall ones listed-Festive Jousing, North Wind Drifter, Ivory Titan, & Navajo Pony are over 40" tall. I don't have any of those, myself, so can't say how well they would grow for you. Plants I have received from Laura have been very nice, you can ask her if they indeed grow as tall as the specs say.
I like taller ones too, don't have very many though, I need to add some. I can recommend one that is fairly new to my garden but I'm impressed with it-Final Frontier, it is a very late bloomer too.
