I wanted to provide info on dealing with my rear brake recently, it's something that was long overdue.
I implemented the recommended solution offered by several here of relocating the reservoir to under the rear seat. I simply reused my existing one and I realize that depending on the different models, some may have more space back there than others. Mine has almost zero to fully enclose that reservoir but I managed to get it to fit just barely and be able to get the seat the latch properly when down.
I went the cheapest route possible and purchased Gates heater hose #28408 which I found at O'reilly auto parts here in the US. You will need 5 feet, I know that sounds like a lot but trust me you'll need it. The main thing is that this is an EPDM hose and was cheap at $1.40/foot. This hose is thicker than the standard OEM brake hose you might be used to, which is a bit of a pain to get it to fit into tight spaces, but a couple of advantages are that it will not kink and will be very resistant to heat near the engine. The hose is 5/8" OD, so make sure to get some new clamps while you're there.
I routed mine the same way as the original brake line to the stock location of the reservoir, but after that I ran it on top of the ABS unit. I cut a notch into the plastic housing of the unit to let the hose run through once the fuel tank sits down on top. I also put some thick vinyl electrical tape onto the sides where I cut it just so that over time the plastic doesn't start cutting into the hose. Once you cut the notch out, you can then route it upward along the frame and use some ties to hold it into location on the side because when you fit the fairing over the frame there's actually plenty of room inside the fairing for the hose to fit.
After all that was done I followed the bleeding procedure from MV's service bulletin, all the air was from the caliper....go figure. Brake is hard as a rock now.