Lanceleaf Buckthorn (Rhamnus lanceolata)

Q: I picked up a great-looking Rhamnus lanceolata at your Kirkwood Market booth a oouple of weeks ago and as it's blooming now, I can see that it is a male plant. I'm putting together another order that I'd like to pick up this coming Saturday and I'd really like to add a couple more of the buckthorns but only if I could be sure to have a female included. Any chance? From what I can tell, the genders are fairly easy to distinguish. THANKS!