Well you can try playing "Electrician" above as KirbyLux77 said.
Personally I don't like all the rust collecting in there and think that heavy moisture exposed it at some point is drastically shortening its overall life.
I don't know how close your local vacuum shops are but hopefully there are a few within a 30 minute or so radius of you. You could show up with your power head or call and see if they have any refurbed or replacement direct connect quick release neck equipped Kenmore power nozzles to fit a bagged Progressive canister. You may even be able to text or email over a photo to them and they could do the same with their selection!
It definitely sounds like you know what you're doing with a vacuum. Don't blame yourself for this, if it was gonna die, it was gonna die! There are many things that can go wrong on a Kenmore canister!! Brand new this series canister would have sold new for around $450!! So I don't know what you spent, but it probably wasn't near $400. After all your unit had the telescoping wand, 2 headlights, dirt sensor, variable speed. It was a TOL Kenmore just below their Intuition series and the Intuition although feature packed was not a very durable unit.
I used eBay's advanced search option for checking description and title. I searched several variations of Kenmore and Panasonic for WhisperBelt, Whispertone, Power head, Powerhead, PowerNozzle, Power Nozzle, carpet vacuum head. Nothing currently was below the $40 range with shipping. Most came in around $50-$70 excluding shipping!! Even with that limited selection I found some with missing height adjuster wheels, worn brush roll bristles, missing rear wheels, non locking elbow-- so it won't lock into the upright position, broken clip so that the height adjuster wheels flop down when the power head is lifted off the rug. So I guess the question is: In how good of condition you are willing to deal with if doing eBay? For some of them with some work you could swap your height adjuster wheels, height adjuster assembly or brush roll or headlight unit from current unit. With some others you'll be limited on part switching.
Here is a better one of the batch, but with shipping it still claims $65. For about $30 more you start seeing entire canister vacuums with hose, suction unit and power head on eBay-- but you'd have to look into individual condition of those too!
http://www.ebay.com/itm/KENMORE-Pow...aa19ecb&pid=100005&rk=1&rkt=6&sd=191865198931
I would try calling the repair shops for a refurb! You may be pleasantly surprised by their prices which you wouldn't have to worry about paying shipping and the units would be fully cleaned and serviced coming from a repair shop with decent or new brush rolls and belts!!
I hope this is helpful. Keep us posted and maybe over or after the weekend we can peruse eBay again for newer, better listings?