Best shock for a light weight pop up truck camper

"walking on solid ground feels weird after a longer camping trip."

That's hilarious. And why sailors walk funny... I was a Marine (Still am technically), but after six months on a Med Cruise I know EXACTLY what you are talking about.

I'm another one that drops the front jacks to stabilize. But mine are electric. I can see that being a pain if yours are manual unless you're staying put for a longer period.
Just throwing this out there, others are welcome to schinto on the idea....but what about a pair of jack stands under the tie down arms? Or even some wood blocks and wedges. You wouldn't be putting huge forces on them and it may be enough to take the rocking out.

I always put the jacks down when I was camped in the TC so it was nice and solid.
The best shocks for a heavy load hauling pick-up are probably Bilstein or KYB Monomax. I've had both and I liked the KYB a little better. But, neither is really going to stop the slight movement when you're parked.

That's just what truck campers do. I doubt any shocks will make a big difference. If you are like myself or my wife, you will get used to it - to the point that walking on solid ground feels weird after a longer camping trip.
As said above already, you can lower the rear jacks to the ground when parked to stabilize the camper.
If you want to play it absolutely safe, disconnect the turnbuckles when you do that. That way, if a tire should go flat while the jacks are on the ground, your truck would not hang from the camper.
Do not forget to retract the jacks and fasten the turnbuckles when you leave.

Any TC is going to move a bit when people are walking or moving. With a light weight truck and camper you would notice it a lot more. After a while you might become used to it. The other solution is to lower the jacks every time you camp.