How can I attach an extended wired keyboard to my Alphasmart Neo?

I connected an extended keyboard to the USB port of my Alphasmart Neo and it doesn't work. The manufacturer said there isn't a way to do this, but I suspect there may be some way. If you know a way I can do this without using AC power, please describe the steps for me.

I want to be sure that I'm not creating any type of EMF/RF etc. at my extended keyboard by doing this.

Thank you