Metric LPG fittings, Therm'x heater

[walter1]

I need propane line info. I have a French made Therm’x catalytic wall heater from a 68 AS, I want to install it in my 64 Safari. The line from the heater unit has banjo fitting at heater and metric compression fitting at other end. I need to extend this line about 6 inches with 2 bends. Parts required...metric compression fitting union, tubing, 2 compression fitting nuts w/ferrules. Simple. Where can I find metric tubing and fitting suitable for LPG? It appears to be approximately 3/16 size line but we confirmed the fittings are actually 1.25 metric thread. I have the original piece that adapts this size to standard 3/8 flare tubing in AS but need to extend the small tubing, can’t just reposition adapter and lengthen 3/8 tubing. Any ideas or sources? Thanks, Walter