Here's a pic of my vertical dropout converter that I built and have been using for a week or so now. It cost around $15 and is far cheaper than trying to find a horizontal/track end frame to use.

It would have taken a lot less time to build if I would have been using something other than a hacksaw...definitely not the tool for the job.

I made it out of 1.25" galvy angle iron and use two 3/8" bolts to mount it right into the vertical dropout. I made sure to include two backups to avoid having the whole thing want to tilt forward on me when I pedal. So far it has worked flawlessly even after hitting some decent holes in the pavement that about wanted to send me crashing as a result of not continuing to pedal like I should have. Something about hitting bumps/holes always makes me want to stop pedaling. I got to break that bad habit and pedal on through. Granted in the same area right now I'm just trying my best to take the whole lane and avoid the obstacles since I ride through that area everyday/sometimes multiple times a day.