In my earlier post, I mentioned the master cylinder when, in fact, I should have said brake fluid reservoir. Just out of curiosity, would it be possible to use a simple tube to act as the reservoir?

Remove the current reservoir and connecting tube.
Take a new, longer tube and run it up the frame.
Fill it then cap it.

Obviously, you'd have to ensure it had the same capacity as the original. Use clear tube so you can see the level of the fluid or, if you were so inclined, wrap the tube in a braided sheathe to disguise it. (With a lil cutout so you can check the levels.)