You can buy steel braided cable (not just the cover) at some auto parts outlets. Also available are the A/N fittings that are compatible to what you currently have for your propane setup.

Braided cable is not cheap though...expect to pay $30 or more depending on the cost per foot where you shop...although I don't know what length you need...

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2009 ML350 (106K) - Family vehicle
2001 CLK430 Cabriolet (80K) - Wife's car
2005 BMW 645CI (138K) - My daily driver
2016 Mustang (32K) - Daughter's car