Newly coming into the sport from riding sleds, I wanted to see if I could save a few dollars by adding my 2.9 gallon Skidoo Linq gas can to my 800 trail rather then buying rotopax or something else
I used a piece of left over 1/4 inch rigid plastic, Some high strength Velcro with some JB weld, one 10mm by 35mm bolt, black paint (which wore off quickly) so ended up using some driveway crack sealer instead.  A set of LINQ mounting brackets about 25 dollars.

Counter sink drilled the bolt hole in the plastic, which goes into the spare tire whole. Does not have to be counter sunk though. JB weld the Velcro to the engine cover (since next to nothing I found will stick to the engine cover plastic) This holds the can from swiveling.  Attach the can as you would on the snowmobile.

Nice job. I bolted my tool/catch all box with that bolt holes too!👍