The local farm stores sell "upgrade kits" right beside the gas jugs. Consists of a flexible spout and an add on vent with caps. Drill a 1/2" hole for the vent, pop it in, screw on the new spout and good to go. Of course the package is labeled as not for use with gas cans.
Yup, I have several of them, and they are awesome workarounds. However, the good quality high flow ones cost almost half of what a plastic 5 gallon can costs, so these environazis are making me pay 150% the price of what a non-nazi can should cost just to keep from spilling one out of every five gallons on the ground, which is what happens when you use their spouts, which require a three-handed man and a midget to operate.
Also, my fault for not looking carefully, but the last can I bought at Home Despot came with a spout of a different cap diameter than the workaround spouts, so apparently the enviro-nazis are getting wise to the workaround. Luckily this was just a 2.5 gallon can, so it's slightly easier to manipulate than a 5 gallon can. But I still spill.