Its not a satisfactory replacement and only temporary but I'm using a 3/8ths i.d. vinyl hose till I also find one.I did read online somewhere out there in the ether about using a hydraulic line for brakes on a car.It had no further description other that red or orange on the outside and black on the inside.Not much help I know.
For me it doesn't even have to withstand another 25 years just get by for a year or so.I could live with that.
Aftermarket companies like Tucker Rocky and Parts Unlimited sell DOT and non-DOT rated stainless steel brake lines... usually in 1 or 2 inch length incraments. If you have a shop nearby that have their catalogs you can skim through and find them. Note that the brake lines indicated length do not include the end fittings and that the length of the brake line measurment should not be the overall length of your present brake line. So if you're brake line overall measurement is, lets say for example, 12"... you should subtract about 2" for the replacement ss line.