If you are handy at fabrication, it wouldn’t be too hard to make a custom clamp. I made two using 1/2” thick hard rubber pad and .060 steel sheet. But, I love to fabricate stuff.
Of course, it might be much simpler to use a hand-held tube bender and tweak the new line so it will engage the existing factory clamp.
I’ve worked on enough aircraft engines, where everything near the engine vibrates, to know that zip ties and rubber tubing won’t last long. Many an amateur mechanic has tried it, sometimes with disastrous results.
Another solution is to bolt together two rubber-cushioned Adel clamps with one attached to an existing fuel line and the other attached to the new fuel line. They would have to be a solid match for the fuel line diameters to do any good, and may not match the current distance between to two fuel lines. You may be able to bend the clamps to decrease their distance. I'd probably put two double clamps in place, just as a bit of overkill so I wouldn't have to worry about them. The rubber on these clamps should last 5-8 years in this application before it starts to break down.