Can't save 'em all...
So I finally broke down and visited a couple of thrift stores. The few vacuums on display were mostly plasticrap and pretty much beat down, although I did see a Kirby Sentria that at first looked to be in reasonably good shape for $25. The price was reasonable enough to entice me to take a second look but in the end, I decided to leave it behind.
First, the bag was jammed completely full, so full that it probably weighed seven or eight pounds and I was frankly afraid to unzip it for fear of what I would find inside. As I pulled the machine back and forth to listen for the telltale clicking noise of a failing TechDrive, I noticed the nozzle was dragging on the floor, so I raised it and discovered a wobble caused by a missing front wheel and stub axle on the height adjuster side. The brush roll was also in bad shape and the belt was off and probably broken but I didn't look closely enough to see for sure. And just to cap things off (pun intended), it was missing a hubcap from one of the rear wheels. At that point, I just pushed it back up against the wall and walked away.
Yeah, it was likely an easy fix and it would even have been a good buy as a parts donor, had I needed one, but I just didn't. Besides, I've already got a pristine Sentria, along with six other Kirbys. But being the good obsessive compulsive that I am, I did look up online to see how much the parts would cost to fix it and assuming nothing else is wrong with the machine, I would have ended up spending another $15-$20 on it so I'm just going to have to let that one be somebody else's project—that is, if I can get my mind to let go of it.