There are only three shocks that i have heard of that fit the Vert.
First is the DNM shock out of the LXR's if you have reasonably deep pockets this is the shock for you mate. Compression adjust, Micro compression Adjust and a rebound adjustment.
Its gone great in my Lxr and has stood up to 60ft jumps with ease. DNM LXR Linkage Rear Shock, Rebound Compression Adjustable
Second is the Elka shock this is for if you have too much money haha. These are the bee's knees in suspension. Elka MX Race Shock for LXR
And the last one is the shock that is in your bike at the moment. Probably the cheapest out of all of them but will still do the job.
Its kinda hard to find them because of the linkage.
Cheers