Retrofit LED can light
I found a solution.  You can buy these on Amazon:
The are called &quot;Retrofit Recessed Downlight Housing C Clips with Self Tapping Screws for Down Light Can&quot;
You screw them onto the wall of the can, and then you have slots to hold the torsion spring of the LED.
They seem to be available only on Amazon (not even the big box stores) so not an easy thing to find.