Jack Lilley have a picture of the genuine Triumph tool on their website
here, and the Haynes Manual has illustrated instructions for how to carry out the task.
As I posted after I did the 24000 service on mine, I'd go about checking the clearances before you go to the trouble of manufacturing the tool. My Tiger is over 27000 miles and the valves are all still in spec from new. Could buy yourself a bit more time in which to manufacture it :wink: