While it's not possible to add agents from RP_only section to the replication link, there are various methods to get the data across.
1) This simple method require a separate storage to achieve that. Just archive necessary data to the temporary storage device (external disk, NAS, etc), then import that archive on the target Core.
2) This method is trickier, but does not require an additional interim storage. To do that, we need any machine, even a VM, that is currently not protected by this Core. Here are steps:
This will link the protected temp machine to the existing RP chain. Now machine can be added to the outgoing replication link and replicate normally. Once replication is done, protection can be removed and agent software can be uninstalled from it.