Doesn't seem to be a common or convenient solution for that particular problem. The subject was raised not long ago and there is supposedly a grommet included in a variety pack from HF or NT that does the trick, or maybe McMaster-Carr? Can't remember exactly. Rich Dougan used to sell a grommet/fuel line combination kit for 10-10's but doesn't seem to be active with that stuff any more. If you still have the original fuel line and it only weeps at the tank opening but is still good otherwise, I've heard guys having success using a few wraps of Teflon tape. I think someone else may have come up with an arrangement of multiple diameters of fuel lines until getting the right combination to make both a tight O.D. and I.D. seal. A real pain in the ass without a handy solution any way ya look at it. Finding a source for the right grommet would be like gold for the 10-10's. Maybe Dougan will give up his source if someone asks him real polite like? LOL