Call up your closest local organic certified farm market. Inquire about by-weekly delivery, (its a good option) Cheeeeeeep!
Once a week, pre-blend. And freeze it for convenience. Put it in the fridge the night before, presto! ready to go! Or take it on the road and use it to cool the contents of your lunch.
Or, If you prefer, make it fresh as you need it.
Every recipe imaginable is free on-line.
Don't buy in to the convenience of your local juice bar. Utterly irrational nonsense. (time, energy, fuel, mark-up, and likely, an inferior product)