My friend has been a cosplay photographer for our cosplay group for the past few years now and she is hoping to do some work while at conventions.
She uses professional grade equipment and is great at getting high quality shots of people. She is willing to negotiate her rates and works very flexibly with people. I have personally been getting cosplay photos taken by her for four years now and have never once been anything but pleased.
Here are some sites showing her work.[link] -Message her here if you're interested.[link][link][link] And here are her rates.10 minutes: $51 Hour: $30
And here is a list of conventions she attends.
(The list may be longer or shorter depending on the year)