It came with 2 radiator style hose clamps about 2" in diameter and some zip ties. It also came with 2 identical rubber pieces. One side has the curvature of the reservoir the other side has the curvature of a 5/8" pipe or so.
How about using the 2 rubber pieces and one hose clamp and securing it to the left side rear foot peg bracket just to the inside of the peg. Keep in mind the chain guard must be on so the chain and hose do not come in contact.
That way looks good. The way Chris mounted it kinda looks like it should be a NOS bottle. The other way looks like they used the zip ties to hold the reservoir and the hose in place on the rear peg mounting bracket.