Yamaha has some nerve selling these at such a price considering the polyethylene oil tank will last foreever.
There is only two reasons to need one, when installing a new tank (BRACKET COMES WITH IT) and replacing one from rust.
At the most each should be 35 bucks and include the top piece.
Beat them at their own game, make your own box as I suggested in another post or use a battery box as above, Just keep the tank from sliding around in box. Add some shims of starboard, anything. No need for top on box. If you want a strap over top (don't really need one), buy a cheap life jackert oin sale and rip off the strap.
There is absolutely no reason a box will not work, don't need the crazy formed bracket. The formed bracket allows one to readily check oil level visually, but it's easy enough to add a vertical slot in box on two sides across from each other and use a 3 buck Home Dept LED flashlite shining thru from one side to see level on the other side. Or just stand the lite on top pointing down, works well enough.
As a tip, I fully caulked my original bracket to the floor to keep out water underneath, so far so good, 5 yrs no rust (to speak of) yet, and the tanks are in the bilge.