All it is a thread coller, a couple O-rings to be used between the shock body and the shock, and two pairs of Eibach Linear rate race springs. Really they probably have less than $150 bucks in the kit itself. I would think you could have this made. Also the KYBS and Bilstiens cost about the same around 375 for all 4 shocks.
I have the GC kit and KYBs along with the other stuff that goes along with it and it helped quite a bit and I am very happy with it. Though without swaybars in the equation the cars is a little sloppy.
The only thing I don't like about that setup is if you catch alot of air your could have the collar slide up and down a bit so a small tack weld or jb weld to hold it down would be ideal.