Don't know any fix for carb cans other than getting fuel cans that are not carb compliant. Non-carb cans may not be legal where you live, there are more states adopting the not supposed to spill a drop cans that seem to have the ability to keep gasoline from going where you want it to go. Have not seen any non-carb replacement spouts that will interchange with the carb cans.

For the cans you have a large funnel will work well for fuel fillers located on top of equipment. The large equipment funnels are available from a well stocked hardware store or a place like tractor supply. For fueling your wife's mini cooper, seem to remember the fuel filler being on the drivers side, put a towel on the roof. Set the can on the towel, don't want to scratch the paint on your wife's ride otherwise you will be sleeping in the garage. I would not recommend this for a tall vehicle, to difficult to lift a full fuel can that high. Open everything up and use one of the HF shaker syphons, i use the surplus jerry cans and this empties the can in around a minute. Or use the pump you have by installing a length of flexible tubing to the output tube.

There are also smaller barrel pumps than the HF ones. I have seen small all plastic, won't rust pumps that the race car crowd uses. There is a cap below the pump designed to fit directly on the square racing gas cans. These things are not what i would call inexpensive but i'm not sure that there is much price difference between this and the wedco cans. The pumps are also by-directional turn the handle one way and it empties the can turn the handle the other way to pump fuel into the can. Very handy to remove the old fuel from the generator.

http://www.flofast.com/products.html

HTH's