I don't know if there is a script, but you can do this.
Go to Devices / Device Management.
open the device in question, and click on "device" to the left of "routing".
In the System section there is a Inventory / View option. click that.
on the network module tab, there will be the base serial number. hover over it to see the full serial number. this is the chassis serial number.
If you find a script, please let me know. I would love to be able to do that as well.
I have attached a screenshots of the locations.
