I think it all comes down to here on tractor you want to mount it, before one can suggest a design for one, there are dozens of ways to make a holder as well as ways one can be mounted
if you go to youtube you will find tons of videos on how to make holders
I have made a few , but again, not sure where on your tractor you want to mount it to really suggest an idea to you!, like insice a cab, outside , is it an enclosed cab or not< front of tractor or back, side or??
like I said, all comes down to what the tractor has that things can be mounted too and where you want it to, suggest a design!
also, there are, a lot of ATV holders will work as well, and some are fairly cheap to buy if you didnlt want to make one
but here is a video you may find interesting on just a HOLDER for the saw, and then you can MAYBE think of where you want to place/mount it??
but if not this video, do a search, LOTS of videos on there to pick from!