I ended up using
81-243, though I think
81-255 would have worked also. The mirror door now slides easily - keeps going when you give it a push.
Removing the old rollers and installing the new ones was a real pain. They fit into a tight space inside the door - I needed to "stretch" the door with one hand while I pushed the roller into the space. I used soap to help lubricate the roller mechanism a bit. You just have to keep at it. I think I read where someone else use disassembled the bottom of the door as an easier way to install. I didn't try that.
I also had trouble removing the screw that held the old rollers. It had been there for at least a decade, maybe two or three. I found a screw driver that had a good fit, then used a pair of plyers to rotate the screw driver. That worked.
Also, the screw has to be aligned with both the roller and a sort of half screw hole that runs above the roller. You can't see it - but with a little trail and error you can get it right - you know when there is resistance.
Lots of grunts and fidgeting, but very doable.