Plastic and/or nylon tubing cannot be used; it cannot hold the high hydraulic pressure of modern braking systems and is not heat resistant (as an aside in the 70's you could actually buy special hard black nylon brake line tubing for non-power assisted brake systems but it vanished from the market as braking systems improved). The other issue is that every time you hit the brake pedal the hose will try to both straighten out and expand rather than transfer fluid and pressure and this will cause a very soft brake pedal. Note you will be legally and morally culpable if you (or a subsequent owners of the vehicle) has a brake failure and someone is injured or killed due to the use of non-OEM brake lines or after-market identical specification lines. Replacing the whole line with an OEM line is the optimal and preferred solution. Yes; you can buy metal bundy brake line tubing and suitable joiners (or the correct diameter and metal type if you know these specs) from Repco and brake specialist but I would be getting a complete new OEM line even if from a wreckers.
Nylon brake lines are still used in some racing application (especially speedway bikes where weight is a factor and lines are short with gentle curves) but are not suitable or legal in street use e.g.
https://www.speedwaymotors.com/Speed...-Kit,1993.html and
https://www.ianboettcherraceparts.co...-ALL48018.html Even with these you have to very careful how they are routed because of there tendency to straighten rather than transfer pressure when the brakes are applied.