Try some JB weld, clean up the area of the break and build up all around the broken bracket. The side cases have been factory clear coated so you will need to sand the clear coat off first before sticking it all together with the JB weld.

I ended up replacing it after trying to patch the crack. I used the low temperature aluminum solder rod form Harbor Freight which worked ok but looked kind of crappy. The thing I really didn't like was that I ended up burning off some of the clear coat on the side cover while doing the repair and had to rattle can black paint to cover up the repair and burnt clear. The aluminum side cover was such a good heat sink that I wasn't able to use my little propane torch, had to get the oxy-aceteylene set out for some real heat to get the rod to flow. The aluminum rod works great on smaller stuff but it was a lot of work on the side cover. I ended up dropping a thrust washer down between the flywheel and stator as I was putting the repaired side cover back on and didn't realize it untill the bike was back together and started. By then I was blessing the POS with everything I could think of. It made a loud whirring as the washer rubbed on the inside of the flywheel, kind of like the starter was engaged. I put about 5 miles on it and tore it back apart. Ended up getting a new side cover and washer from Royayers. While I was in there the second time I slotted the mounting holes on the ignition sensor and was able to bump the timing up by about 2 degrees. Seems to of given the engine another 250-300rpm at the top end, by then I was looking for a way to blow it up which luckly didn't happen. It would pretty easy to make a bracket for the sensor to get more spark advance, I just got tired of fooling around with it.