You need a time machine, snoop at garage sales or find someon willing to part with one.
Edit: or you can get the goofy amazon ones
ORANDESIGNE Flexible Gas Can Spouts Replacement and Vents Kit Ultra Long Fuel Tank Nozzle with Filter Screen 2 Collar Screw Cap for Pre 2009 Plastic Gas Can Kerosene Water Jug 1 2 5 Gallon Pack of 3 https://www.amazon.com/dp/B07YKVKZ9Z/ref=cm_sw_r_cp_api_i_Y4vzEbCJF2FQ5