You don't carry an inflatable gas can in your vehicle?
Some people use a wide-mouth oil container. It needs to be rinsed with throttle body cleaner, first. Of course, the washer fluid containers are illegal for gasoline, and I wouldn't want washer fluid in my fuel.
The gas cans at the gas stations here are about $5. Dunno if that is high. If it were up to the gas stations, they probably wouldn't carry gas cans, but the cans are a means to help them sell gas. The overhead is very high, because the cans take a lot of space, and mostly just sit and collect dust. The retail space is very valuable. Think how many high-profit, fast-moving items, like lighters, candy bars, or other items could fit in that space. When I was traveling, recently, I do not recall seeing any gas cans at any gas stations--not that I was looking for one.