generator isolators

I think the word you want is "dampers"
Aka Rubber Mounts, or spring mounts
Yeah the seller called them Isolators

They should support the generator , but should have some give so as to absorb the vibration
In my experience, big soft round donut style,
Hole in the middle No built in mounting stud
Work best
Those in your link are more like stiff rubber feet you screw onto the bottom of the generator

Around these forums
Isolator is used to mean 12vdc power and battery separation

I think you need a solid base for the dampers to work well and the platform hanging off the rear of your camper is anything but.

Obviously I have no idea what I am doing, search for
dampers did help a bit. Am now trying to figure out hardness scales to find something soft. Not a lot of people around that know about isolators/dampers.

Years ago I had an old beat up garden tractor that had a bone jarring ride, I cut a couple rubber balls in half,, added them, worked wonders! May have to do the same thing here. I am returning the Amazon isolators, not much help at all.

Lots of people know about them: Vibration damper design

I'll bet an AC supply company would have just what you need (attic furnace/blower) installs.

Damping is the key word and adding mass is the key to calming the damping effect. It would add significant weight but building a concrete form to pour about 2" to 3" thick block just larger than the generator base. You will need to carefully position 4 holes in the block just to keep the genny from dancing around. You still may be able to use the feet you are showing.

In my prior life I had 3 large squirrelcage, combustion air, blowers about 50" diameter, driven by 75 hp motors. The shaft bearings were mounted on fabricated steel frames about 4-1/2ft. tall, made of 5/8" welded steel. I could not keep the pedestal bearings from self destruction, no matter how carefully the fans were balanced. I finally had holes burned in the side of the pedestal housings and filled them with concrete. Had lots of non-believers but this magically solved the problem.

Vibration Isolators Somehow you'll have to figure out how to choose one that isn't too soft or too hard.

there is a bunch of different ones here Floor Mount Vibration Isolators

Durometer is the measure of how firm the rubber is. A durometer around 60 is about the hardness of a car tire. The higher the number the firmer the rubber. my guess is something around a 40 to 50 durometer is what you're looking for,

I got mine at McMaster Carr. Many types available.