Where is the leak in the reservoir? If it's like mine, there is a gasket in the cover, and my gasket became hard over time, allowing the fluid to leak. I replaced the gasket, and all is well.

Also, if that's not the problem and they definitely won't pay for the fix, you might want to try some of the stop leak stuff you can buy in auto parts stores. It's at least worth a shot.

Good luck.