I like the NATO military style cans, and there are many places that sell new and true surplus cans in many different styles. They’re rugged and leakproof, and the spout for the 20 liter cans can be used on the smaller sizes as well. The cap/spout gasket is replaceable.
In addition to Lexington Container above, there is also:
Atlantic British (Land Rover parts)
WavianJerrycan.comOne place that your search engine may miss is
Swiss Army Vehicles in Fayetteville, AR. They’re a distributor of European military vehicles, parts and surplus, and they have some of the best prices on jerrycans around. Click on the “Army Surplus” tab to find them.
When I bought my four cans several years ago, they were selling true NATO surplus cans at great prices. I’m in Fayetteville often enough that I could drop by and pick through their stock for the best ones. It looks like they’re selling new cans now, and you will have a hard time finding better prices. They do run out of them though, so you may have to watch their website for a while. It appears they have at least some to sell right now. If you’re in the area, drop by and you can also look at some of those cool military vehicles they sell.
I always carry a 20L can of Diesel fuel on the rear bumper of the camper. I have occasionally had to use it. I also need to carry a small can of gasoline for the Yamaha 1000 I always have with us, so I bought a 5L can from Atlantic British. That’s where I got the 20L can holder you can see in the picture below (just the black frame, the rest is repurposed material from my junk pile) and the spouts I’m using.

:):)