Like everyone else says, do this at your own risk.
I saw an old golf bag carrier at the thrift store for $6 and worked out this project with materials in my garage.
I removed all the plastic bag holding stuff, straightened the kick out of the bottom end, and shortened up the handle and re attached it with self tapping metal screws. I love them for projects. I had some extruded "T" aluminum and made the frame out of it. At first tried aluminum solder, but as I was working one joint popped and I teck screwed all the rest. To mount the frame to the bag cart I drilled an tapped 1/4-20 long screws and through bolted it. I reinforced the frame with struts fitting into the cart frame at the wheels. I built a bed out of corrugated plastic light panels. I had to splice a piece with sticks and clear 2 inch tape to make it fill the bed. I attached this with 3M industrial spray adhesive. I worked out the universal joint incorporating the hallow handle, fabricated "U" piece through bolted with 1/4-20 threaded stock and aircraft nuts for up and down motion. Attached to the "U" piece is an angle through bolted in the center with 1/4-20 hardware including aircraft nut for yaw movement. Then the angle piece is through bolted to the custom center hitch on the bike for turning movement. I used a 3/8 bolt with a hole drilled at the correct height to lock in the nut with a fast removable "hair pin" for ease of hook up. This was a typical project of mine such that it was a work in progress with modifications as I went along. It isn't completely finished because it needs an enclosure. I am trying to acquire an old car top clam-shell cargo carrier to mount on the frame and bed. The trailer rides really well and is very light weight. This is my first instructable, sorry it it isn't very clear. Thanks. Also I noticed the comment boxes shift from my original edit. After correcting them a couple time they seem to go where they want to.