I've seen ad's for such a beast in the past in magazines, and now I need one but can't find one of those ads

- so I'm wondering if anyone else has any info on this critter. The best I can describe it is - it's a two wheel affair like a hand truck, but it has a trailer ball on it - designed to slide under the trailer tongue, push down on the handles and you can maneuver the trailer around by hand. Anybody seen or heard of something like this? Thanks for info in advance guys!
Jim