Problem with buying a kit....you will be tied to how that kit wants mounted. ie length of bars etc.

Speak to any of the following, and in no particular order.

Andy Robinson Race cars
Hauser Racing
Webster Engineering.

Or...speak to any local cage prep guy. He should be able to supply you tube of varying diameters so you could fab them yourself.
or he could maybe fab you the mounts etc.

Just find a suitable bush, then have sleeves made up to mount those bushes. Most of the yank axle kits will be rose jointed ( and rose joints are noisy and annoying as I discovered )

This is a basic 4 link kit, parallel bars. The above people would be able to supply. You could adapt so the top bars are no longer parallel, which would sort the lateral axle movement.

http://www.jegs.com/i/Competition+En.../2017/10002/-1

The pic above isnt actually a great design anyway, wouldnt be hard to improve. And box section just looks nasty