You can't get a true lemoyne star with HST's, unfortunately.
Another option is a template set I own. Marti Michele's Perfect Patchwork Templates, Set H (Large Hexagon plus) comes with 2 diamond templates, One for 1.5 " diamonds and one for 3" diamonds. You could get 2 different sizes of lemoyne stars from those - but you'd have to work out the setting blocks yourself, so maybe that's not such a great idea. oops.
But she has set E - lemoyne stars:
http://www.frommarti.com/eandf.shtml
Maybe that's what you need.