I had my 4th gen gas filler neck replaced under MaxCare. I had this problem. The newer neck design has less of an angle, and makes it easier to put the nozzle in and remove.
For my motorcycle, I just ordered the following. I haven't tested it yet, but it would work the same as the toilet gasket:
McCuff Motorcycle Fill and Tank Protector
I'm not sure of what the difference is between sport and v-twin, but I got the v-twin model. I think it has to do with a sportbike gas cap swinging open, and not having a lot of room around it.