Hello Kelly,
I am a lurker on the flyrotary forum. For some reason I haven’t been able to get subscribed to be able to post but I read on the web.
You could try a pump from aquamist in the UK.
They make water injection systems for cars. I have used their pumps successfully in the past. Its high pressure.
http://www.aquamist.co.uk/
cheers
Mike Wynn