Hey, I’m also looking for front brakes lines for an early rebel (1985 250) and the pickings do seem slim. What I’ve seen is a lot of parted out brake assemblies online going for cheep, though quality is my concern with that. Oem and aftermarket seems hard to find for early models but someone mentioned to me that you could even swap out newer model parts with older bikes since they haven’t changed all that much. Maybe have them look for aftermarket but for the newer models?
I’m in the same boat with my 250. From my research, if you go stainless, you can buy all the bits individually and assembly it. The only “tricky” part is figuring out which angle fittings to use on the end. The good news is that they’re not expensive and there are lots of choices. For the 250, there are some posts on this forum that give what fittings work best for various years.
Also reminder: the 250s switched sides the brake is on, so make sure to know what you’re getting.
Watch the video they offer and take your time. Requires strength and precision to build properly. Stainless steel is more challenging to work with, it loosens easily with increased handling. Cut ~1/2" more so you have a but to restart if necessary. You will see what I mean.