RE: Kangke Waco Biplane
Twin flyer, you may have to shop around a bit. Here are places I know of that may have it.
Karting supply shops, chemical supply companies ( may not sell in small quatities less than 55 gallon drums) , performance automotive retailers and shops, agriculteral fuel supply facilities, bulk fuel suppliers, performance engine builders to name a few.
If the chemical supply companies won't sell in small quantities they might tell you if some of their customers will.
Good luck'