I use a Blitz brand plastic can with a Mike Sr (Redline) cap and it works very well.
What I do is use a 2 Gallon can for mixing my fuel, 1 pint oil (16 fl oz) per 1.6 gallons of gas and a little Marine Stabil. I store fuel in this jug with it tightly capped.
At the pond I use the 1 gal blitz can with the Mike Sr. cap and MPI fuel pump.
I don't fill either can much over 1/2 of its capacity espically at this time of year with the large temperature swings. There is most likely a pressure build up because of temperature change causing your gas to seep out..