Write to the monastery and see if they will send you some seeds. They may have developed an extra-tall variety.
Have you determined yet whether you are allowed to import seeds by mail to Israel? If you can, I'm sure you will be able to find some folks who will send you seeds of any type of zinnia you want on this site.
Tall zinnias would be quite top-heavy once they are in bloom. I can visualize tall zinnias growing in a walled garden of a monastery where they would get lots of sun and care, and also would be protected from the wind by the walls.
Stone walls also collect heat during the day and keep the plants warmer at night so this would extend their growing season - they could start plants earlier, and keep them going into the fall weather longer. This is known as a "micro-climate".
