Mine works fine. I'd take it apart and see if the slide tracks need cleaned and lubed, and wiper on them needs a little springiness put back in. It could even be that a well directed shot of WD-40 fixes it by thinning out hardened grease a bit if it's petroleum rather than silicone based grease.
Any small automotive grade mechanical potentiometer is going to have wear problems over time, and due to the type and way it's integrated into the mirror form factor, no way to upgrade it to a premium industrial grade part like you could with a standard round panel mount potentiometer.
Anyway, I think your only hope besides DIY repair or replacement with another slider type is to scavenge the forums to see if anyone reports doing it differently, as it isn't a common thing to have someone try to put a radically different mirror (controls) on. If you are insistent on doing it, you may just need to rewire it to work instead of expecting plug and play, but I bet they're all using a slide switch. Who wants a knob sticking out on their mirror?
Another alternative would be to trace the relevant wires and tap into them under the dash, wiring up a separate remotely mounted potentiometer and a switch if not so integrated, then mount it on the dash, on a bracket just under the dash, or on the center console.
