When I checked with Yuneec about a year ago they still had several hundred sets left in stock. I ordered mine direct from Yuneec’s sales department.
Order at least two packages of PN YUNGB603001. They come 6 dampers with safety pins per package. The CGO-4 should have three dampers per gimbal corner, for a total of 12. The GB603 only used 1 per corner IRRC.
Make sure the gimbal thumb screws are tight or the mount can introduce vibration. Just a head's up, you won't be able to get rid of all the jello at full zoom but post stabilization programs work great.