I use a Trailer Dollly from Harbor Frieght that I picked up on sale for $50, ugly but has worked well. I have to get my rusted tongue extension fixed so that I can give that a try.
I thing Richie's idea is also viable. It would be simple to extend the handle as long as you need it. Attach a coupler to it an attach it to your hitch ball. The extension doesn't have to be that big. 1 1/2" square tubing would work. The load is under tension and that should be strong enough. It would be steerable and should support the tongue just fine.
I would have gone that route if I had thought of it, but went with a retractable extender 12' that fits under the towing tongue. I do have a 6" swivel wheel welded under the receiver tube on the trailer tongue. The picture shows a 12" wheel that doesn't swivel. The original intent was to use that to back straight down the ramp. The 6" swivel wheel allows me to tow back to the storage with the extender out. I've got it down so that I can hook up and launch in about 10 minutes. At the bow the water is about 4' deep.
My ramp has a 6:1 slope. With the 12' extension and 18' from hitch to axle. The axle is 30' down the ramp making it about 5' deep.
With this set up I can launch easily with little hassle. I only tow about 100 yds so I leave the extension out when towing. I use to block the wheels and pull the extension out at the ramp but that was too much work. I decided one day to see if I could park it in mast up with the extension out and found I could. Saves me a lot of time and jumping in and out of the truck.
Some of the stuff I see at the ramp would scare the heck out of me but it seems to work for some of these guys with fin keels. They use all kinds of ropes and straps. I watched one guy pull his ski doo out with a motor cycle attached to his trailer. He gunned it and took off. He got up to the parking lot and stopped. The skidoo was going like a bat out of hell headed right toward him. Fortunately it turned just before running him over and went on for another 50'.
Here is a picture of my set up. It won't work for you but a variation would. As posted earlier Timo42 has a great setup on his Mac 22.