@Elena, There are NO seeds to buy. The plant does not produce seeds. Please save your money.
I think buying the plant material through your local florist, while not the least expensive choice, may be the best. Do you have experience with floral design? (No, I am not volunteering my services, sorry.) Upstate New York is beautiful in the Fall. Why not convince the bride (yeah, right) to go with Fall colors. Way less expensive.
I'm good - no fall allergies, only allergic to the southern pine pollen. I used to live 50 miles from NYC and often drove the car into the city to go shopping; thanks for the invite.
Gosh, I need to buy new clothes! My hair! My nails...

just kidding.