You can make your own orgeat syrup by boiling a tablespoon of water and tablespoon of almonds in 1/4 cup of water until they reduced to a thick syrup. You can also buy pre-made orgeat syrup (almond simple syrup) at any specialty grocer.
If you are making these for a party, assemble garnishes ahead of time on cocktail picks and store in a plastic container in the fridge until ready to serve.