Heck I had to figure out what you were trying to ask, and what an Avon 7 was. I would say it is going to take more in tools and materials, then spending the 80 euros. Do you own a welder? Tig or mig if you do? What about a tubing bender? Probably could build one without bending tubing though. You will still need the tubing for the mount though. If you plan to run in salt water do you care if it rusts? Steel is much cheaper than stainless.
A simple google search turned up a couple of photos.
