I’m assuming here that you have the vCenter database on the same server as vCenter as that’s the normal install process.
Spin up a second VM and install vCenter on it with it’s own database installed locally. Using vCenter join the two vCenter servers together so that they both manage the environment (VMware has documented how to do this, it’s pretty straight forward but I don’t have the doc in front of me handy). Now if one fails the other vCenter machine will just take over.
You’ll want to use DRS to configure a rule to keep these two VMs away from each other so that they never end up on the same piece of hardware.