not sure how far you've gone as regards purchase of O.E.M. item (not cheap) but I would normally sit down and carefully measure "O" ring seat dimensions plus new and/or s/hand fitted "O" ring as a guideline before ordering a range, With an extensive search you might already find someone who can recommend a source that's impervious to Ethanol but I can't access my notes right now. .https://www.motorcyclespareparts.eu/en/yamaha-parts/3ld141470000
