Copy a Linode between accounts?
While there is not a way to copy a Linode to another account directly from the Manager, there are a couple of ways you could go about doing this once you've resized your Linode.
The first method is to clone your Linode to another, and then request that we transfer the new copy to the other account. Once the clone has been made, you can open a ticket on both accounts - one requesting that the Linode and any additional services be transferred, and one accepting the transfer and the cost of the Linode and its services moving forward.
The second option is to create a Linode on another account, configure it, and copy its data by using any of a number of available file transfer methods, but be conscious of how much data you are sending, as it will count against your Network Transfer quota.