Sorry about the USB. My Ipad hasn't arrived yet, but on its way. Anyway, a buddy does use his Ipad(ver1) with a GPS puck, I didn't realize it wasn't a USB connector, although, I just looked up that they make an adapter. I hadn't looked that closely at his.
Are you talking about the Apple Camera Connection Kit ($29). If your friend is able to get a puck gps to work over the connection kit...*PLEASE SHARE DETAILS*....this would be a dream setup for me.
Otherwise, I'm not aware of any GPS (other than the Bad Elf) that works directly with the proprietary apple connection (the really wide one).