Bobby, there are a lot of problems with that, that I can see. The first is the cost. All you need is a frame attached to the bike with a wheel on it.
The trike frame would have to have the sprocket removed and the top braces removed so you can mount the sidecar lower to the ground. Then you need to weld a frame to the trike frame so that you can mount the sidecar and hook it up to the bike.
If you look at the other sidecar thread you will see how I built mine. The next one I will use angle iron but the square tubing was at the house and free so I used it. Old bed frames would be a good source and free if you get lucky or cheap at the Goodwill store.. Bolting it together using nylon lock nuts if you don't have a welder would work.
My next body will be made using 1/4 inch luan plywood since it is cheap, bendable and light. You may have to pedal it some day. Plywood base and a 2X4 frame to give the sidecar shape. You can build a very nice sidecar with simple hand tools and basic power tools like a saber saw.
My thoughts are that you can put a finish on it many ways. Stain the wood with a stain colour you like and 6-10 coats of water based, gloss spar varnish with a foam brush. Three coats and then sand it with 400 wet or dry paper. Your choice of wet or dry. Lightly sand every coat after that just to knock down the nibs and provide a tooth for the next coat. I'd use the paper dry.
Next to last coat I'd sand it until it is dead flat with little or no shiney spots. The last coat should come out dead smooth and shiney. Wait a couple of months in warm weather and buff it to a blinding shine if you wish.
Hey, I restored antique furniture for 43 years. I make it soud easy and it is..
The next is glue canvas to it using wood glue and then paint it. Gives a nice textured finish. Apply the glue with a 3-4 inch, short haired, roller. Gives a nice even coat that way.
Last is find some very thin sheetmetal and cut and prefit the panels to the sidecar and then glue the panels to the sidecar with contact cement with the roller. When dry, paint your colour.
I'm thinking about making a video but then I'd have to clean up the work shop and that would take a while.
Steve.