I wanted to ask if any of the mechanics here could recommend a good replacement 7-speed mountain rear derailleur. The rest of my drivetrain is Shimano Deore DX with SIS thumbshifters (yes, we're talking circa 1992) and I do not ride off-road at all...this bike is solely for commuting to/from work. That said, I do ride pretty hard and have a huge hill every day coming home...so I simply want to find a replacement derailleur that works well and won't fall apart.

Thanks for your help.