I hear that 'she pee' urinals were a big hit for women at Glasto this year - same principal as the 'wee wagon' but for us girlies and ideal when you just need to do a quick stand-up pee and get the hell out of it, as opposed to a sit-down (or hover above) in a portaloo , which can be hellishly complicated, specially in the dark.
Actually, I think that you'll find a 'lenor' bottle is perfect for ladies and gents. It has a particularly wide neck you see making it easier for you to 'position' when you're a girlie. Plus if you leave a teensy bit of lenor in the bottom it smells nice (and it has the added bonus of a screw top)! Most supermarkets off some sort of 'value' lenor stuff so you might be able to get one cheap. I think I've had a Tesco one for 34p before- hurrah! Much cheaper than some options on here