I bought my new black plastic line from ebay seller mattzyx , current listing.....
eBay item number:
153175973581
Mates up OK with the gauge.
NOTE THAT the new line has different style fittings at either end (IIRC!!) - one tapered, and one with a flat face + small fibre washer I think.
And then an adapter from ENZED pipe people for the join between metal engine pipe and that end of the new line.
Make sure you take the engine metal line and the new plastic one with you to the shop !!!
I decided I was pushing my luck after 48 years on the original (now hard) plastic line.
Good luck