Made a bit of mistake here in that Waldmeister is made with Woodruff rather then Linden. Americans can get it here: http://www.germandeli.com/rawawsy50.html
and the price is cheap which is nice. Also, this stuff is great over ice and mixed with milk. Lots of people use this various German biers as well. Lastly, I know that a lot of people have used fennel syrup in the same way in both drinks and moassel so that is worth looking into as well.