How much does 1 jet size affect A/F?

I've just finished making the jet and rod changes but it's dark out now, so I'll have to wait till tomorrow (if weather permits) to take it for a spin. I seem to have overtightened the banjo fuel fitting again (yep happened before) and the plastic gasket seems to have been compressed too much, a little bit of a fuel drip while running.

Does anyone know if I can just get a plastic gasket from a hardware store or are those not resistant to fuel? I'll call a performance place around here in the morning to see if they have one but in case I'm SOL it would be nice to have an alternative.