Hey so I know you posted this months ago, but I also just ran into this problem so I figured I'd add my $0.02.
When I ordered my struts, mounts, and boot kits, I totally forgot about the spring insulators. Whoops. So yeah, I had just what was left of my 32 year old rubber insulators to work with when I reassembled the new struts. The first thing I did was push them as deeply into the space they are meant to go as possible, mostly to try and squeeze all the frayed and ripped bits to a spot that'd have them under the spring. Then I soaked them all down with a ton of silicone spray (get it at the parts store in a can), which I've found works pretty well to re-condition old plastic and (to a lesser extent) rubber. I also used small amounts of spray on gasket-stick type stuff when I was compressing the springs, to help me shove the rubber bits into a good spot. All in all it's pretty ugly, but I do have no metal-on-metal contact above or below any of my 4 springs. Mission sort of accomplished?
Then I did some google-fu and came across this:
https://teamenergysuspension.com/energy-products/automotive/universal/universal-coil-spring-isolators/Haven't tried to order anything yet so no idea if you can actually get your hands on these, but it seems to be precisely what we need. I was going to wait until I ordered a set of H&R springs to figure out what part numbers we would need, but I do have all my old struts and mounts easily available at the moment. I could probably figure out which would work best just with that stuff, if you want.