Howdy All,
Get someone to draw it on CAD and then get it laser cut. If you get a bunch of them done they will be as cheap as chips. We get stuff like that done at work all the time.
Alternatively for DIY people.
1) make a pattern in timber
2) cut the shape roughly out in the aluminium plate with a bandsaw or jig saw
3)Attach the rough shape to the pattern and rout around it with a ball bearing guide bit.
Fairly simple. Once you have the pattern you can make as many as you want and the finish is better than laser cut plate. Only problem is the minimum internal radii is the diameter of the router bit.
You will see a mounting plate for a Givi top box I made the same way somewhere on this site. Looks great. (if i do say so myself)
