I'd consider getting an bounce/shoot through umbrella and a light stand. They're great for working outdoors (if wind isn't an issue...)
For this shot I bounced out of a photoflex 45" umbrella with a 580 ex ii (photoflex umbrellas are wonderful- fiberglass ribs instead of thin metal). I shot it wide with a 16-35mm 2.8 ii, and adjusted the flash and exposure to make the background darker to isolate the subject.
Second shooter actually happened to get this pic showing the umbrella and stand. It was back just far enough to be outside the frame and sitting just to my left. I raised the umbrella a little taller than her and then pointed it down at her.